Date: July 11, 1989 X3T9.2/89-094R1 To: X3T9.2 Committee (SCSI) From: George Penokie (IBM) Subject: 16 Bit Data Path on a Single 68 pin Connector Section 4 Issues -Termination of the cable -Terminating resistor values Should be adjusted to allow a lower cable impedance and to reduce the tramission line reflections as much as possible. -Drive current maximum Should be made greater then 48ma, possibilly 96ma or 72ma depending on what can be realisticly provided by the chip manufacturers. -Cable length change If the current is increased then the Cable length should be lengthened to reflect the increased current of the drivers. -The maximum number of devices Should be make to be 16 if the W cable is used. Section 5 Issues -Some wording changes in section 5.1.2 ARBITRATION Phase are required to indicate there are now 16 devices allowed on the bus. -Some changes in section 5.1.5.3 Wide Data Transfer are required to indicate there is another cableing option. Section 7 Issues -The copy commands segment Descriptor does not have room for a 4 bit source address and a 4 bit destination address. -Make byte 1 bit 4 of the segment descriptor a high/low address range indicator for the destination address. Where 0 is the low address range and 1 is the high address range. Make byte 1 bit 5 of the segment descriptor a high/low address range indicator for the source address. Where 0 is the low address range and 1 is the high address range. Section 8, 9, 10, 12, 13, 14, 15, and 16 Issues -The Release command and Reserve command do not have room for a 4 bit third party device ID -Make 10 byte commands for both the Release and Reserve commands Section 4 changes recommened to implement a single 68 pin connector 4. Physical Characteristics This section contains the physical definition of SCSI-3. The connectors, cables, signals, terminators, and bus timing values needed to implement the interface are covered. 4.1. Physical Description SCSI devices are daisy-chained together using a common | 50-conductor A cable and, optionally, a 68-conductor B cable, or a | common 68-conductor W cable. Both ends of all cables are terminated. All signals are common between all SCSI devices on | the A cable and on the W cable. In systems that employ the B cable wide SCSI option, wide SCSI devices additionally connect to the B cable. Various width SCSI devices may be mixed on A cable B | cable systems. Verious width SCSI devices may be mixed on W cable | systems, however, all devices shall have 68-conductor connections. Two driver/receiver alternatives are specified for A/B cable systems: (1) Single-ended drivers and receivers, which allow a maximum cable length of six meters (primarily for connection within a cabinet). (2) Differential drivers and receivers, which allow a maximum cable length of 25 meters (primarily for connection outside of a cabinet). | Two driver/receiver alternatives are specified for W cable | systems: (1) Single-ended drivers and receivers, which allow a | maximum cable length of ___ meters (primarily for connection | within a cabinet). (2) Differential drivers and receivers, which | allow a maximum cable length of __ meters (primarily for | connection outside of a cabinet). | (Need to decide if the cable length will change for the W cable | option) | The single-ended and differential alternatives are mutually | exclusive within a system. The A/B cable and W cable alternatives | are mutually exclusive within a system. IMPLEMENTORS NOTE: Use of single-ended drivers and receivers with the fast synchronous data transfer option is not recommended. 4.2. Cable Requirements  | An ideal impedance match with cable terminators on an A/B cable | system implies a cable characteristic impedance of 132 ohms | (singled-ended option) or 122 ohms (differential option). The | cable characteristic impedance shall be no less than 90 ohms and | no greater than 140 ohms. It is recommended that the cable | characteristic impedance be greater than 100 ohms for all cable | types. See 4.2.3 for cable requirements when implementing the | fast synchronous data transfer option. An ideal impedance match with cable terminators on an W cable system implies a cable characteristic impedance of ___ ohms (singled-ended option) or ___ ohms (differential option). The cable characteristic impedance shall be no less than __ ohms and no greater than ___ ohms. It is recommended that the cable characteristic impedance be greater than ___ ohms for all cable types. See 4.2.3 for cable requirements when implementing the fast synchronous data transfer option. A minimum conductor size of 0.08042 mm2 (28 AWG) should be used to minimize noise effects and ensure proper distribution of terminator power. IMPLEMENTORS NOTES: (1) To minimize discontinuities and signal reflections, cables of different impedances should not be used in the same bus. Implementations may require trade-offs in shielding effectiveness, cable length, the number of loads, transfer rates, and cost to achieve satisfactory system operation. (2) To minimize discontinuities due to local impedance variation, a flat cable should be spaced at least 1.27 mm (0.050 in) from other cables, any other conductor, or the cable itself when the cable is folded. (3) Regulatory agencies may require use of larger wire size. 4.2.1. Single-Ended Cable A 50-conductor flat cable or 25-signal twisted-pair cable shall be used for the A cable. A 68-conductor flat cable or 34-signal twisted-pair cable shall be used for the B cable if the wide SCSI | option is implemented and for the W cable. If twisted-pair cables are used, then twisted pairs in the cable shall be wired to physically opposing contacts in the connector. A stub length of no more than 0.1 meters is allowed off the mainline interconnection within any connected equipment. IMPLEMENTORS NOTE: Stub clustering should be avoided. Stubs should be spaced at least 0.3 meters apart. SCSI bus termination may be internal to the SCSI devices that are at the ends of the cable. 4.2.2. Differential Cable A 50-conductor flat cable or 25-signal twisted-pair cable shall be used for the A cable. A 68-conductor flat cable or 34-signal twisted-pair cable shall be used for the B cable if the wide SCSI | option is implemented and for the W cable. If twisted-pair cables are used, then twisted pairs in the cable shall be wired to physically opposing contacts in the connector. A stub length of no more than 0.2 meters is allowed off the mainline interconnection within any connected equipment. SCSI bus termination may be internal to the SCSI devices that are at the ends of the cable. IMPLEMENTORS NOTE: The use of twisted pair cable (either twisted-flat or discrete wire twisted pairs) is strongly recommended. Without twisted pairs, even at slow data rates and very short distances, crosstalk between adjacent signals causes spurious pulses with differential signals. 4.2.3. Cable Requirements for Fast Synchronous Data Transfer In systems which use the fast synchronous data transfer option (see 4.8), The A, B, and W cables should consist of conductors of at least 0.08042 mm2 (28 AWG). The cable should have an overall shield suitable for termination in a shielded connector. In such systems, the A and B cables shall have the following electrical characteristics: Characteristic Impedance: 90 to 132 ohms Signal Attenuation: 0.095 dB maximum per meter at 5 MHz Pair-to-Pair Propagation Delay Delta: 0.20 ns maximum per meter DC Resistance: 0.230 ohms maximum per meter at 20 degrees C | In such systems, the W cable shall have the following electrical | characteristics: Characteristic Impedance: __ to ___ ohms Signal | Attenuation: _.___ dB maximum per meter at _ MHz Pair-to-Pair | Propagation Delay Delta: _.__ ns maximum per meter DC Resistance: | _.___ ohms maximum per meter at __ degrees C (Need to decide if | the characteristic impedance will change) 4.3. Connector Requirements Two types of connectors are defined: nonshielded and shielded. The nonshielded connectors are typically used for in-cabinet applications. Shielded connectors are typically used for external applications where electromagnetic compatibility (EMC) and electrostatic discharge (ESD) protection may be required. Either type of connector may be used with the single-ended or differential drivers. 4.3.1. Nonshielded Connector Requirements Two nonshielded connector alternatives are specified for the A cable, one nonshielded connector is specified for the B cable and | one nonshielded commector is specified for the W cable. 4.3.1.1. Nonshielded Connector Alternative 1 - A Cable The alternative 1 nonshielded high-density SCSI device connector for the A cable (Figure 4-1) shall be a 50-conductor connector consisting of two rows of 25 female contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. The alternative 1 nonshielded high-density cable connector for the A cable (Figure 4-2) shall be a 50-conductor connector consisting of two rows of 25 male contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. 4.3.1.2. Nonshielded Connector Alternative 2 - A Cable The alternative 2 nonshielded low-density SCSI device connector for the A cable (Figure 4-3) shall be a 50-conductor connector consisting of two rows of 25 male pins with adjacent pins 2.54 mm (0.1 in) apart. A shroud and header body should be used. The nonmating portion of the connector is shown for reference only. The alternative 2 nonshielded low-density cable connector for the A cable (Figure 4-4) shall be a 50-conductor connector consisting of two rows of 25 female contacts with adjacent contacts 2.54 mm (0.1 in) apart. It is recommended that keyed connectors be used. | 4.3.1.3. Nonshielded Connector - B Cable and W Cable The nonshielded high-density SCSI device connector for the B | cable and for the W cable (Figure 4-1) shall be a 68-conductor connector consisting of two rows of 34 female contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. The nonshielded high-density cable connector for the B cable and | for the W cable (Figure 4-2) shall be a 68-conductor connector consisting of two rows of 34 male contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. 4.3.2. Shielded Connector Requirements Two shielded connector alternatives are specified for the A | cable and one shielded connector is specified for the B cable and | one shielded connector is specified for the W cable. The connector shielding system should provide a dc resistance of less than 10 milliohms from the cable shield at its termination point to the SCSI device enclosure. In order to support daisy-chain connections, SCSI devices that use shielded connectors should provide two shielded device connectors on the device enclosure. These two connectors may be wired "one-to-one" with a stub to the SCSI device's drivers and receivers provided the maximum stub length is not violated. Alternatively, two cables may be run from the two shielded connectors to the drivers and receivers so that the maximum stub length is not violated. The length of the cable within the device enclosure is included when calculating the total cable length of the SCSI bus. IMPLEMENTORS NOTE: SCSI-1 defined three shielded connector systems in an appendix. The alternative 1 shielded connector of SCSI-1 has been replaced by a high-density connector in this standard. The alternative 2 shielded connector remains unchanged. The EUROCARD Boxes shielded connector system of SCSI-1 has been deleted in this standard. 4.3.2.1. Shielded Connector Alternative 1 - A Cable The shielded high-density SCSI device connector for the A cable (Figure 4-5) is a 50-conductor connector consisting of two rows of 25 female contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. The shielded high-density cable connector for the A cable (Figure 4-6) is a 50-conductor connector consisting of two rows of 25 male contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. 4.3.2.2. Shielded Connector Alternative 2 - A Cable The shielded low-density device connector for the A cable (Figure 4-7) is a 50-conductor connector consisting of two rows of ribbon contacts spaced 2.16 mm (0.085 in) apart. The nonmating portion of the connector is shown for reference only. The shielded low-density cable connector for the A cable (Figure 4-8) is a 50-conductor connector consisting of two rows of ribbon contacts spaced 2.16 mm (0.085 in) apart. The nonmating portion of the connector is shown for reference only. | 4.3.2.3. Shielded Connector - B Cable and W Cable The shielded high-density SCSI device connector for the B cable | and for the W cable (Figure 4-5) is a 68-conductor connector consisting of two rows of 34 female contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. | The shielded high-density cable connector for the B cable and | for the W cable (Figure 4-6) is a 68-conductor connector consisting of two rows of 34 male contacts with adjacent contacts 1.27 mm (0.05 in) apart. The nonmating portion of the connector is shown for reference only. Figure 4-1: 50/68-Contact Nonshielded High-Density SCSI Device Connector | (A Cable/B Cable/W Cable) Figure 4-2: 50/68-Contact Nonshielded High-Density Cable Connector | (A Cable/B Cable/W Cable) Figure 4-3: 50-Contact Nonshielded Low-Density SCSI Device Connector (A Cable) Figure 4-4: 50-Contact Nonshielded Low-Density Cable Connector (A Cable) Figure 4-5: 50/68-Contact Shielded High-density SCSI Device Connector | (A Cable/B Cable/W Cable) Figure 4-6: 50/68-Contact Shielded High-density Cable Connector | (A Cable/B Cable/W Cable) Figure 4-7: 50-Contact Shielded Low-Density SCSI Device Connector Figure 4-8: 50-Contact Shielded Low-Density Cable Connector 4.3.3. Connector Contact Assignments The connector contact assignments are defined in Tables 4-1 through 4-7. Table 4-1 defines which of the other four tables to use and which set of contact assignments to use. Table 4-1: Cross-Reference to Connector Contact Assignments ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Driver/ Contact Receiver Connector Assignment Contact Connector Type Type Cable Figure Table Set ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Nonshielded Alternative 1 Single-Ended A 4-1 & 4-2 4-2 2 Nonshielded Alternative 1 Single-Ended B 4-1 & 4-2 4-3 |Nonshielded Alternative 1 Single-Ended W 4-1 & 4-2 4-4 Nonshielded Alternative 1 Differential A 4-1 & 4-2 4-5 2 Nonshielded Alternative 1 Differential B 4-1 & 4-2 4-6 |Nonshielded Alternative 1 Differential W 4-1 & 4-2 4-7 Nonshielded Alternative 2 Single-Ended A 4-3 & 4-4 4-2 1 Nonshielded Alternative 2 Differential A 4-3 & 4-4 4-5 1 Shielded Alternative 1 Single-Ended A 4-5 & 4-6 4-2 2 Shielded Alternative 1 Single-Ended B 4-5 & 4-6 4-3 |Shielded Alternative 1 Single-Ended W 4-5 & 4-6 4-4 Shielded Alternative 1 Differential A 4-5 & 4-6 4-5 2 Shielded Alternative 1 Differential B 4-5 & 4-6 4-6 |Shielded Alternative 1 Differential W 4-5 & 4-6 4-7 Shielded Alternative 2 Single-Ended A 4-7 & 4-8 4-2 2 Shielded Alternative 2 Differential A 4-7 & 4-8 4-5 2 ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Table 4-2: Single-Ended Contact Assignments - A Cable ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Connector Cable Connector Signal Contact Number Conductor Contact Number Signal Name Set 2 Set 1 Number Set 1 Set 2 Name ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GROUND 1 1 1 ³ 2 2 26 -DB(0) GROUND 2 3 3 ³ 4 4 27 -DB(1) GROUND 3 5 5 ³ 6 6 28 -DB(2) GROUND 4 7 7 ³ 8 8 29 -DB(3) GROUND 5 9 9 ³ 10 10 30 -DB(4) GROUND 6 11 11 ³ 12 12 31 -DB(5) GROUND 7 13 13 ³ 14 14 32 -DB(6) GROUND 8 15 15 ³ 16 16 33 -DB(7) GROUND 9 17 17 ³ 18 18 34 -DB(P) GROUND 10 19 19 ³ 20 20 35 GROUND GROUND 11 21 21 ³ 22 22 36 GROUND RESERVED 12 23 23 ³ 24 24 37 RESERVED OPEN 13 25 25 ³ 26 26 38 TERMPWR RESERVED 14 27 27 ³ 28 28 39 RESERVED GROUND 15 29 29 ³ 30 30 40 GROUND GROUND 16 31 31 ³ 32 32 41 -ATN GROUND 17 33 33 ³ 34 34 42 GROUND GROUND 18 35 35 ³ 36 36 43 -BSY GROUND 19 37 37 ³ 38 38 44 -ACK GROUND 20 39 39 ³ 40 40 45 -RST GROUND 21 41 41 ³ 42 42 46 -MSG GROUND 22 43 43 ³ 44 44 47 -SEL GROUND 23 45 45 ³ 46 46 48 -C/D GROUND 24 47 47 ³ 48 48 49 -REQ GROUND 25 49 49 ³ 50 50 50 -I/O ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTES: (1) The minus sign next to a signal indicates active low. (2) The conductor number refers to the conductor position when using 0.050- inch centerline flat ribbon cable with a low-density connector or when using 0.025-inch centerline flat ribbon cable with a high-density connector. Other cable types may be used to implement equivalent contact assignments. (3) Two sets of contact assignments are shown. Refer to Table 4-1 to determine which set of contacts applies to each connector. (4) See 4.4.4 for a definition of the RESERVED lines. Table 4-3: Single-Ended Contact Assignments - B Cable ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Connector Cable Connector Signal Contact Conductor Contact Signal Name Number Number Number Name ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GROUND 1 1 ³ 2 35 GROUND GROUND 2 3 ³ 4 36 -DB(8) GROUND 3 5 ³ 6 37 -DB(9) GROUND 4 7 ³ 8 38 -DB(10) GROUND 5 9 ³ 10 39 -DB(11) GROUND 6 11 ³ 12 40 -DB(12) GROUND 7 13 ³ 14 41 -DB(13) GROUND 8 15 ³ 16 42 -DB(14) GROUND 9 17 ³ 18 43 -DB(15) GROUND 10 19 ³ 20 44 -DB(P1) GROUND 11 21 ³ 22 45 -ACKB GROUND 12 23 ³ 24 46 GROUND GROUND 13 25 ³ 26 47 -REQB GROUND 14 27 ³ 28 48 -DB(16) GROUND 15 29 ³ 30 49 -DB(17) GROUND 16 31 ³ 32 50 -DB(18) TERMPWRB 17 33 ³ 34 51 TERMPWRB TERMPWRB 18 35 ³ 36 52 TERMPWRB GROUND 19 37 ³ 38 53 -DB(19) GROUND 20 39 ³ 40 54 -DB(20) GROUND 21 41 ³ 42 55 -DB(21) GROUND 22 43 ³ 44 56 -DB(22) GROUND 23 45 ³ 46 57 -DB(23) GROUND 24 47 ³ 48 58 -DB(P2) GROUND 25 49 ³ 50 59 -DB(24) GROUND 26 51 ³ 52 60 -DB(25) GROUND 27 53 ³ 54 61 -DB(26) GROUND 28 55 ³ 56 62 -DB(27) GROUND 29 57 ³ 58 63 -DB(28) GROUND 30 59 ³ 60 64 -DB(29) GROUND 31 61 ³ 62 65 -DB(30) GROUND 32 63 ³ 64 66 -DB(31) GROUND 33 65 ³ 66 67 -DB(P3) GROUND 34 67 ³ 68 68 GROUND ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTES: (1) The minus sign next to a signal indicates active low. (2) The conductor number refers to the conductor position when using 0.025- inch centerline flat ribbon cable. Other cable types may be used to implement equivalent contact assignments. | Table 4-4: Single-Ended Contact Assignments - W Cable | |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Connector Cable Connector | Signal Contact Conductor Contact Signal | Name Number Number Number Name |ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ | GROUND 1 1 ³ 2 35 GROUND | GROUND 2 3 ³ 4 36 -DB(0) | GROUND 3 5 ³ 6 37 -DB(1) | GROUND 4 7 ³ 8 38 -DB(2) | GROUND 5 9 ³ 10 39 -DB(3) | GROUND 6 11 ³ 12 40 -DB(4) | GROUND 7 13 ³ 14 41 -DB(5) | GROUND 8 15 ³ 16 42 -DB(6) | GROUND 9 17 ³ 18 43 -DB(7) | GROUND 10 19 ³ 20 44 -DB(P) | GROUND 11 21 ³ 22 45 GROUND | GROUND 12 23 ³ 24 46 -ATN | GROUND 13 25 ³ 26 47 -BSY | GROUND 14 27 ³ 28 48 -ACK | GROUND 15 29 ³ 30 49 GROUND | GROUND 16 31 ³ 32 50 -RST | TERMPWR 17 33 ³ 34 51 TERMPWR | TERMPWR 18 35 ³ 36 52 TERMPWR | GROUND 19 37 ³ 38 53 -MSG | GROUND 20 39 ³ 40 54 -SEL | GROUND 21 41 ³ 42 55 -C/D | GROUND 22 43 ³ 44 56 -REQ | GROUND 23 45 ³ 46 57 -I/O | GROUND 24 47 ³ 48 58 GROUND | GROUND 25 49 ³ 50 59 -DB(8) | GROUND 26 51 ³ 52 60 -DB(9) | GROUND 27 53 ³ 54 61 -DB(10) | GROUND 28 55 ³ 56 62 -DB(11) | GROUND 29 57 ³ 58 63 -DB(12) | GROUND 30 59 ³ 60 64 -DB(13) | GROUND 31 61 ³ 62 65 -DB(14) | GROUND 32 63 ³ 64 66 -DB(15) | GROUND 33 65 ³ 66 67 -DB(P1) | GROUND 34 67 ³ 68 68 GROUND |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTES: (1) The minus sign next to a signal indicates active low. (2) The conductor number refers to the conductor position when using 0.025- inch centerline flat ribbon cable. Other cable types may be used to implement equivalent contact assignments. Table 4-5: Differential Contact Assignments - A Cable ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Connector Cable Connector Signal Contact Number Conductor Contact Number Signal Name Set 2 Set 1 Number Set 1 Set 2 Name ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GROUND 1 1 1 ³ 2 2 26 GROUND +DB(0) 2 3 3 ³ 4 4 27 -DB(0) +DB(1) 3 5 5 ³ 6 6 28 -DB(1) +DB(2) 4 7 7 ³ 8 8 29 -DB(2) +DB(3) 5 9 9 ³ 10 10 30 -DB(3) +DB(4) 6 11 11 ³ 12 12 31 -DB(4) +DB(5) 7 13 13 ³ 14 14 32 -DB(5) +DB(6) 8 15 15 ³ 16 16 33 -DB(6) +DB(7) 9 17 17 ³ 18 18 34 -DB(7) +DB(P) 10 19 19 ³ 20 20 35 -DB(P) DIFFSENS 11 21 21 ³ 22 22 36 GROUND RESERVED 12 23 23 ³ 24 24 37 RESERVED TERMPWR 13 25 25 ³ 26 26 38 TERMPWR RESERVED 14 27 27 ³ 28 28 39 RESERVED +ATN 15 29 29 ³ 30 30 40 -ATN GROUND 16 31 31 ³ 32 32 41 GROUND +BSY 17 33 33 ³ 34 34 42 -BSY +ACK 18 35 35 ³ 36 36 43 -ACK +RST 19 37 37 ³ 38 38 44 -RST +MSG 20 39 39 ³ 40 40 45 -MSG +SEL 21 41 41 ³ 42 42 46 -SEL +C/D 22 43 43 ³ 44 44 47 -C/D +REQ 23 45 45 ³ 46 46 48 -REQ +I/O 24 47 47 ³ 48 48 49 -I/O GROUND 25 49 49 ³ 50 50 50 GROUND ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTES: (1) The conductor number refers to the conductor position when using 0.050- inch centerline flat ribbon cable with a low-density connector or when using 0.025-inch centerline flat ribbon cable with a high-density connector. Other cable types may be used to implement equivalent contact assignments. (2) Two sets of contact assignments are shown. Refer to Table 4-1 to determine which set of contacts applies to each connector. (3) See 4.4.4 for a definition of the RESERVED lines. Table 4-6: Differential Contact Assignments - B Cable ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Connector Cable Connector Signal Contact Conductor Contact Signal Name Number Number Number Name ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GROUND 1 1 ³ 2 35 GROUND +DB(8) 2 3 ³ 4 36 -DB(8) +DB(9) 3 5 ³ 6 37 -DB(9) +DB(10) 4 7 ³ 8 38 -DB(10) +DB(11) 5 9 ³ 10 39 -DB(11) +DB(12) 6 11 ³ 12 40 -DB(12) +DB(13) 7 13 ³ 14 41 -DB(13) +DB(14) 8 15 ³ 16 42 -DB(14) +DB(15) 9 17 ³ 18 43 -DB(15) +DB(P1) 10 19 ³ 20 44 -DB(P1) +ACKB 11 21 ³ 22 45 -ACKB GROUND 12 23 ³ 24 46 DIFFSENS +REQB 13 25 ³ 26 47 -REQB +DB(16) 14 27 ³ 28 48 -DB(16) +DB(17) 15 29 ³ 30 49 -DB(17) +DB(18) 16 31 ³ 32 50 -DB(18) TERMPWRB 17 33 ³ 34 51 TERMPWRB TERMPWRB 18 35 ³ 36 52 TERMPWRB +DB(19) 19 37 ³ 38 53 -DB(19) +DB(20) 20 39 ³ 40 54 -DB(20) +DB(21) 21 41 ³ 42 55 -DB(21) +DB(22) 22 43 ³ 44 56 -DB(22) +DB(23) 23 45 ³ 46 57 -DB(23) +DB(P2) 24 47 ³ 48 58 -DB(P2) +DB(24) 25 49 ³ 50 59 -DB(24) +DB(25) 26 51 ³ 52 60 -DB(25) +DB(26) 27 53 ³ 54 61 -DB(26) +DB(27) 28 55 ³ 56 62 -DB(27) +DB(28) 29 57 ³ 58 63 -DB(28) +DB(29) 30 59 ³ 60 64 -DB(29) +DB(30) 31 61 ³ 62 65 -DB(30) +DB(31) 32 63 ³ 64 66 -DB(31) +DB(P3) 33 65 ³ 66 67 -DB(P3) GROUND 34 67 ³ 68 68 GROUND ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTE: The conductor number refers to the conductor position when using 0.025- inch centerline flat ribbon cable. Other cable types may be used to implement equivalent contact assignments. | Table 4-7: Differential Contact Assignments - W Cable | |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Connector Cable Connector | Signal Contact Conductor Contact Signal | Name Number Number Number Name |ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ | GROUND 1 1 ³ 2 35 GROUND | +DB(0) 2 3 ³ 4 36 -DB(0) | +DB(1) 3 5 ³ 6 37 -DB(1) | +DB(2) 4 7 ³ 8 38 -DB(2) | +DB(3) 5 9 ³ 10 39 -DB(3) | +DB(4) 6 11 ³ 12 40 -DB(4) | +DB(5) 7 13 ³ 14 41 -DB(5) | +DB(6) 8 15 ³ 16 42 -DB(6) | +DB(7) 9 17 ³ 18 43 -DB(7) | +DB(P) 10 19 ³ 20 44 -DB(P) | GROUND 11 21 ³ 22 45 GROUND | +ATN 12 23 ³ 24 46 -ATN | +BSY 13 25 ³ 26 47 -BSY | +ACK 14 27 ³ 28 48 -ACK | GROUND 15 29 ³ 30 49 DIFFSENS | +RST 16 31 ³ 32 50 -RST | TERMPWR 17 33 ³ 34 51 TERMPWR | TERMPWR 18 35 ³ 36 52 TERMPWR | +MSG 19 37 ³ 38 53 -MSG | +SEL 20 39 ³ 40 54 -SEL | +C/D 21 41 ³ 42 55 -C/D | +REQ 22 43 ³ 44 56 -REQ | +I/O 23 45 ³ 46 57 -I/O | GROUND 24 47 ³ 48 58 GROUND | +DB(8) 25 49 ³ 50 59 -DB(8) | +DB(9) 26 51 ³ 52 60 -DB(9) | +DB(10) 27 53 ³ 54 61 -DB(10) | +DB(11) 28 55 ³ 56 62 -DB(11) | +DB(12) 29 57 ³ 58 63 -DB(12) | +DB(13) 30 59 ³ 60 64 -DB(13) | +DB(14) 31 61 ³ 62 65 -DB(14) | +DB(15) 32 63 ³ 64 66 -DB(15) | +DB(P1) 33 65 ³ 66 67 -DB(P1) | GROUND 34 67 ³ 68 68 GROUND |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ NOTE: The conductor number refers to the conductor position when using 0.025- inch centerline flat ribbon cable. Other cable types may be used to implement equivalent contact assignments. 4.4. Electrical Description For the measurements in this section, SCSI bus termination is assumed to be external to the SCSI device. SCSI devices may have the provision for allowing optional internal termination. 4.4.1. Single-Ended Alternative All signals not defined as RESERVED, GROUND, or TERMPWR shall be terminated at both ends of the cable. The implementor may choose one of the following two methods to terminate each end of an A/B cabled system: (1) The termination of each signal shall consist of 220 ohms (+/-5%) to the TERMPWR line and 330 ohms (+/-5%) to ground (see Figure 4-9). Using resistors with +/-1% tolerance improves noise margins. (2) The termination of each signal shall meet these requirements: (a) The terminators shall each supply a characteristic impedance between 100 and 132 ohms. (b) The terminators shall be powered by the TERMPWR line and may receive additional power from other sources but shall not require such additional power for proper operation (see 4.4.3). (c) The current available to any signal line driver shall not exceed 48 milliamps when the driver asserts the line and pulls it to 0.5 volts dc. Only 44.8 milliamps of this current shall be available from the two terminators. (d) The voltage on all released signal lines shall be at least 2.5 volts dc when the TERMPWR line is within specified values (see 4.4.3). (e) These conditions shall be met with any legal configuration of targets and initiators as long as at least one device is supplying TERMPWR. | All signals not defined as RESERVED, GROUND, or TERMPWR shall be | terminated at both ends of the cable. The implementor may choose | one of the following two methods to terminate each end of a W | cabled system: | | (1) The termination of each signal shall consist of ___ ohms | (+/-5%) to the TERMPWR line and ___ ohms (+/-5%) to ground (see | Figure 4-9). Using resistors with +/-1% tolerance improves noise | margins. | | (2) The termination of each signal shall meet these | requirements: | (a) The terminators shall each supply a characteristic | impedance between ___ and ___ ohms. | (b) The terminators shall be powered by the TERMPWR line and | may receive additional power from other sources but shall not | require such additional power for proper operation (see 4.4.3). | (c) The current available to any signal line driver shall not | exceed __ milliamps when the driver asserts the line and pulls it | to 0.5 volts dc. Only __._ milliamps of this current shall be | available from the two terminators. | (d) The voltage on all released signal lines shall be at least | 2.5 volts dc when the TERMPWR line is within specified values (see | 4.4.3). | (e) These conditions shall be met with any legal configuration | of targets and initiators as long as at least one device is | supplying TERMPWR. 4.4.1.1. Output Characteristics All signals shall use open-collector or three-state drivers. Each signal driven by an SCSI device shall have the following output characteristics when measured at the SCSI device's connector on an A/B calbed system: VOL (Low-level output voltage) = 0.0 to 0.5 volts dc at 48 milliamps sinking (signal assertion) VOH (High-level output voltage) = 2.5 to 5.25 volts dc (signal negation) | All signals shall use open-collector or three-state drivers. | Each signal driven by an SCSI device shall have the following | output characteristics when measured at the SCSI device's | connector on a W calbed system: | VOL (Low-level output voltage) = 0.0 to 0.5 volts dc at __ | milliamps sinking (signal | assertion) | VOH (High-level output voltage) = 2.5 to 5.25 volts dc | (signal negation) 4.4.1.2. Input Characteristics SCSI devices with power on shall meet the following electrical characteristics on each signal (including both receivers and passive drivers): VIL (Low-level input voltage) = 0.0 to 0.8 volts dc (signal true) VIH (High-level input voltage) = 2.0 to 5.25 volts dc (signal false) IIL (Low-level input current) = -0.4 to 0.0 milliamps at VI = 0.5 volts dc IIH (High-level input current) = 0.0 to 0.1 milliamps at VI = 2.7 volts dc Minimum input hysteresis = 0.2 volts dc Maximum input capacitance = 25 pF (measured at the device connector closest to the stub, if any, within the device) It is recommended that SCSI devices with power off also meet the above IIL and IIH electrical characteristics on each signal. 4.4.2. Differential Alternative All signals consist of two lines denoted +SIGNAL and -SIGNAL. A signal is true when +SIGNAL is more positive than -SIGNAL, and a signal is false when -SIGNAL is more positive than +SIGNAL. All assigned signals of the A and B cables described in 4.6 shall be terminated at each end of the cable with a terminator network as shown in Figure 4-10. Resistor tolerances in the terminator network shall be +/-5% or less. The DIFFSENS signal of the connector is used as an active high enable for the differential drivers. If a single-ended device or terminator is inadvertently connected, this signal is grounded, disabling the differential drivers (see Figure 4-11). 4.4.2.1. Output Characteristics Each signal driven by an SCSI device shall have the following output characteristics when measured at the SCSI device's connector on an A/B cabled system: VOL (Low-level output voltage) = 1.7 V maximum at IOL (Low-level output current) = 55 milliamps. VOH (High-level output voltage) = 2.7 V minimum at IOH (High-level output current) = -55 milliamps. VOD (Differential output voltage) = 1.0 V minimum with common-mode voltage ranges from -7 to +12 volts dc. | Each signal driven by an SCSI device shall have the following | output characteristics when measured at the SCSI device's | connector on a W cabled system: | VOL (Low-level output voltage) = 1.7 V maximum at IOL | (Low-level output current) = __ milliamps. | VOH (High-level output voltage) = 2.7 V minimum at IOH | (High-level output current) = -__ milliamps. | VOD (Differential output voltage) = 1.0 V minimum with | common-mode voltage | ranges from -7 to +12 | volts dc. VOL and VOH shall be as measured between the output terminal and the SCSI device's logic ground reference. The output characteristics shall additionally conform to ISO 8482. 4.4.2.2. Input Characteristics SCSI devices shall meet the following electrical characteristics on each signal (including both receivers and passive drivers): II (Input current on either input) = +/- 2.0 milliamps maximum. Maximum input capacitance = 25 pF. The II requirement shall be met with the input voltage varying between -7 and +12 volts dc, with power on or off, and with the hysteresis equaling 35 millivolts, minimum. The input characteristics shall additionally conform to ISO 8482. 4.4.3. Terminator Power SCSI initiators shall supply terminator power to the TERMPWR contact(s) and, if it implements the wide SCSI option, to the TERMPWRB contacts. This power shall be supplied through a diode or similar semiconductor that prevents backflow of power to the SCSI device. Targets and SCSI devices that become temporary initiators (e.g., targets which implement the COPY command or asynchronous event notification) are not required to supply terminator power. Any SCSI device may supply terminator power. All terminators independent of location shall be powered from the TERMPWR and TERMPWRB contact(s). The use of keyed connectors is recommended in SCSI devices that provide terminator power to prevent accidental grounding or misconnection of terminator power. IMPLEMENTORS NOTE: Regulatory agencies may require limiting maximum (short circuit) current to the terminator power lines. Recommended current limiting is one amp for TERMPWR and two amps for TERMPWRB. For systems utilizing multiple initiators, the initiators may be configured with option straps or current limiting devices. Maximum available current should not exceed five amps. SCSI devices shall sink no more than 1.0 milliamp from TERMPWR and no more than 1.0 milliamp from TERMPWRB except to power an optional internal terminator. Single-ended SCSI devices providing terminator power on cable A shall have the following characteristics: VTerm = 4.25 to 5.25 volts dc 900 milliamps minimum source drive capability Differential SCSI devices providing terminator power on cable A shall have the following characteristics: VTerm = 4.0 to 5.25 volts dc 600 milliamps minimum source drive capability | Single-ended SCSI devices providing terminator power on cable | B and on cable W shall have the following characteristics: | VTerm = 4.25 to 5.25 volts dc | 1500 milliamps minimum source drive capability | Differential SCSI devices providing terminator power on cable | B and on cable W shall have the following characteristics: | VTerm = 4.0 to 5.25 volts dc | 1000 milliamps minimum source drive capability Figure 4-9: Termination for Single-Ended Devices Figure 4-10: Termination for Differential Devices Figure 4-11: Differential Driver Protection Circuit 4.4.4. RESERVED Lines The lines labeled RESERVED in the A cable contact assignment tables (Table 4-2 and Table 4-4) shall be connected to ground in the bus terminator assemblies or in the end devices on the SCSI cable. The RESERVED lines should be open in the other SCSI devices, but may be connected to ground. 4.5. SCSI Bus Communication on the SCSI bus is allowed between only two SCSI devices at any given time. There is a maximum of eight SCSI | devices on an A/B cabled system. There is a maximum of 16 SCSI | devices on a W cabled system. Each SCSI device has an SCSI ID bit assigned as shown in Figure 4-12. When two SCSI devices communicate on the SCSI bus, one acts as an initiator and the other acts as a target. The initiator originates an operation and the target performs the operation. An SCSI device usually has a fixed role as an initiator or target, but some devices may be able to assume either role. An initiator may address up to eight peripheral devices that | are connected to a target on an A/B cabled system. An initiator | may address up to 16 peripheral devices that are connected to a | target on a W cabled system. Three sample system configurations are shown in Figure 4-13. DB(7) DB(6) DB(5) DB(4) DB(3) DB(2) DB(1) DB(0) <ÄÄ DATA BUS ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ SCSI ID = 0 ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ SCSI ID = 1 ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ SCSI ID = 2 ³ ³ ³ ³ ³ ³ ³ ³ ³ SCSI ID = 3 ³ ³ ³ ³ ³ ³ ³ SCSI ID = 4 ³ ³ ³ ³ ³ SCSI ID = 5 ³ ³ ³ SCSI ID = 6 ³ SCSI ID = 7 | DB(15) DB(14) DB(13) DB(12) DB(11) DB(10) DB(9) DB(8) <ÄÄ DATA BUS | ³ ³ ³ ³ ³ ³ ³ ³ | ³ ³ ³ ³ ³ ³ ³ SCSI ID = 8 | ³ ³ ³ ³ ³ ³ ³ | ³ ³ ³ ³ ³ ³ SCSI ID = 9 | ³ ³ ³ ³ ³ ³ | ³ ³ ³ ³ ³ SCSI ID = 10 | ³ ³ ³ ³ ³ | ³ ³ ³ ³ SCSI ID = 11 | ³ ³ ³ ³ | ³ ³ ³ SCSI ID = 12 | ³ ³ ³ | ³ ³ SCSI ID = 13 | ³ ³ | ³ SCSI ID = 14 | ³ | SCSI ID = 15 Figure 4-12: SCSI ID Bits Figure 4-13: Sample SCSI Configurations Up to eight SCSI devices can be supported on the SCSI bus on | an A/B cabled system. Up to 16 SCSI devices can be supported on | the SCSI bus on a W cabled system. They can be any combination of initiators and targets. Certain SCSI bus functions are assigned to the initiator and certain SCSI bus functions are assigned to the target. The initiator may arbitrate for the SCSI bus and select a particular target. The target may request the transfer of COMMAND, DATA, STATUS, or other information on the DATA BUS, and in some cases it may arbitrate for the SCSI bus and reselect an initiator for the purpose of continuing an operation. Information transfers on the DATA BUS are asynchronous and follow a defined REQ/ACK handshake protocol. One byte of information may be transferred with each handshake on the A cable and, if the wide data transfer option is implemented, one or two | byte of information may be transfered with each handshake on the W | cable or one or three bytes of information may be transferred with each handshake on the B cable. An option is defined for synchronous data transfer. 4.6. SCSI Bus Signals | There are a total of 18 signals on the A cable, 27 on the W | cable, and 29 signals on the B cable. A total of 11 signals are used for control and 36 are used for data, including parity. These signals are described as follows: BSY (BUSY). An "OR-tied" signal that indicates that the bus is being used. SEL (SELECT). An "OR-tied" signal used by an initiator to select a target or by a target to reselect an initiator. IMPLEMENTORS NOTE: The SEL signal was not defined as "OR-tied" in SCSI-1. It has been defined as "OR-tied" in SCSI-3 in anticipation of needing another "OR-tied" signal for future standardization. This does not cause an operational problem in mixing SCSI-1 and SCSI-3 devices. C/D (CONTROL/DATA). A signal driven by a target that indicates whether CONTROL or DATA information is on the DATA BUS. True indicates CONTROL. I/O (INPUT/OUTPUT). A signal driven by a target that controls the direction of data movement on the DATA BUS with respect to an initiator. True indicates input to the initiator. This signal is also used to distinguish between SELECTION and RESELECTION phases. MSG (MESSAGE). A signal driven by a target during the MESSAGE phase. | REQ (REQUEST). A signal driven by a target on the A cable or the | W cable to indicate a request for a REQ/ACK data transfer handshake. REQB (REQUEST). A signal driven by a target on the B cable to indicate a request for a REQB/ACKB data transfer handshake. ACK (ACKNOWLEDGE). A signal driven by an initiator on the A | cable or the W cable to indicate an acknowledgment for a REQ/ACK data transfer handshake. ACKB (ACKNOWLEDGE). A signal driven by an initiator on the B cable to indicate an acknowledgment for a REQB/ACKB data transfer handshake. ATN (ATTENTION). A signal driven by an initiator to indicate the ATTENTION condition. RST (RESET). An "OR-tied" signal that indicates the RESET condition. DB(7-0,P) (DATA BUS). Eight data-bit signals, plus a parity-bit signal that form a DATA BUS. DB(7) is the most significant bit and has the highest priority during the ARBITRATION phase. Bit number, significance, and priority decrease downward to DB(0). A data bit is defined as one when the signal value is true and is defined as zero when the signal value is false. Data parity DB(P) shall be odd. Parity is undefined during the ARBITRATION phase. DB(31-8,P1,P2,P3) (DATA BUS). Twenty-four data-bit signals, plus three parity-bit signals that form an extension to the DATA BUS. DB(P1,P2,P3) are parity bits for DB(15-8), DB(23-16), and | DB(31-24) respectively. On SCSI devices which support 16 IDs | DB(15) has the highest priority in the db(15-8) byte during the | ARBITRATION phase. The priority decreases downward to DB(8). | DB(15) has a lower priority than DB(0). A data bit is defined as one when the signal value is true and is defined as zero when the signal value is false. Data parity DB(Px) shall be odd. 4.6.1. Signal Values Signals may assume true or false values. There are two methods of driving these signals. In both cases, the signal shall be actively driven true, or asserted. In the case of OR-tied drivers, the driver does not drive the signal to the false state, rather the bias circuitry of the bus terminators pulls the signal false whenever it is released by the drivers at every SCSI device. If any driver is asserted, then the signal is true. In the case of non-OR-tied drivers, the signal may be actively driven false, or negated. In this standard, wherever the term negated is used, it means that the signal may be actively driven false, or may be simply released (in which case the bias circuitry pulls it false), at the option of the implementor. The advantage to actively driving signals false during the information transfer is that the transition from true to false occurs more quickly and the noise margin is much higher than if the signal is simply released; this is required to reliably transfer data at maximum rates, especially at the longer cable lengths used with differential drivers. 4.6.2. OR-Tied Signals The BSY, SEL, and RST signals shall be OR-tied only. In the ordinary operation of the bus, the BSY and RST signals may be simultaneously driven true by several drivers. No signals other than BSY, RST, and DB(P) are simultaneously driven by two or more drivers, and any signal other than BSY, SEL, and RST may employ OR-tied or non-OR-tied drivers. DB(P) shall not be driven false during the ARBITRATION phase. There is no operational problem in mixing OR-tied and non-OR-tied drivers on signals other than BSY and RST. 4.6.3. Signal Sources Table 4-8 indicates which type of SCSI device is allowed to source each signal. No attempt is made to show if the source is driving asserted, driving negated, or is passive. All SCSI device drivers that are not active sources shall be in the passive state. The RST signal may be asserted by any SCSI device at any time. Table 4-8: Signal Sources ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ A Cable Signals B Cable Signals ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ C/D, I/O, MSG, ACK, DB(7-0) DB(31-8), Bus Phase BSY SEL REQ ATN DB(P) REQB ACKB DB(P1,P2,P3) ÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄ BUS FREE None None None None None None None None ARBITRATION All Win None None S ID None None None SELECTION I&T Init None Init Init None None None RESELECTION I&T Targ Targ Init Targ None None None COMMAND Targ None Targ Init Init None None None DATA IN Targ None Targ Init Targ Targ Init Targ DATA OUT Targ None Targ Init Init Targ Init Init STATUS Targ None Targ Init Targ None None None MESSAGE IN Targ None Targ Init Targ None None None MESSAGE OUT Targ None Targ Init Init None None None ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | W Cable Signals | ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ | C/D, | I/O, | MSG, ACK, DB(15-0) | Bus Phase BSY SEL REQ ATN DB(P,P1) | ÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄ ÄÄÄÄÄÄÄ | BUS FREE None None None None None | ARBITRATION All Win None None S ID | SELECTION I&T Init None Init Init | RESELECTION I&T Targ Targ Init Targ | COMMAND Targ None Targ Init Init | DATA IN Targ None Targ Init Targ | DATA OUT Targ None Targ Init Init | STATUS Targ None Targ Init Targ | MESSAGE IN Targ None Targ Init Targ | MESSAGE OUT Targ None Targ Init Init |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ All: The signal shall be driven by all SCSI devices that are actively arbitrating. S ID: A unique data bit (the SCSI ID) shall be driven by each | SCSI device that is actively arbitrating; the other data bits shall be released (i.e., not driven) by this SCSI device. The parity bit(s) (DB(P)) may be released or driven to the true state, but shall never be driven to the false state during this phase. I&T: The signal shall be driven by the initiator, target, or both, as specified in the SELECTION phase and RESELECTION phase. Init: If driven, this signal shall be driven only by the active initiator. None: The signal shall be released; that is, not be driven by any SCSI device. The bias circuitry of the bus terminators pulls the signal to the false state. Win: The signal shall be driven by the one SCSI device that wins arbitration. Targ: If the signal is driven, it shall be driven only by the active target. 4.7. SCSI Bus Timing Unless otherwise indicated, the delay-time measurements for each SCSI device, shown in Table 4-9, shall be calculated from signal conditions existing at that SCSI device's own SCSI bus connection. Thus, these measurements (except cable skew delay) can be made without considering delays in the cable. Table 4-9: SCSI Bus Timing Values ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Arbitration Delay . . . . . . . . 2.4 microseconds Assertion Period . . . . . . . . 90 nanoseconds Bus Clear Delay . . . . . . . . . 800 nanoseconds Bus Free Delay . . . . . . . . . 800 nanoseconds Bus Set Delay . . . . . . . . . . 1.8 microseconds Bus Settle Delay . . . . . . . . 400 nanoseconds Cable Skew Delay . . . . . . . . 10 nanoseconds Data Release Delay . . . . . . . 400 nanoseconds Deskew Delay . . . . . . . . . . 45 nanoseconds Disconnection Delay . . . . . . . 200 microseconds Hold Time . . . . . . . . . . . . 45 nanoseconds Negation Period . . . . . . . . . 90 nanoseconds Power-On to Selection Time . . . 10 seconds recommended Reset to Selection Time . . . . . 250 milliseconds recommended Reset Hold Time . . . . . . . . . 25 microseconds Selection Abort Time . . . . . . 200 microseconds Selection Time-out Delay . . . . 250 milliseconds recommended Transfer Period . . . . . . . . . set during an SDTR message Fast Assertion Period . . . . . . 30 nanoseconds Fast Cable Skew Delay . . . . . . 5 nanoseconds Fast Deskew Delay . . . . . . . . 20 nanoseconds Fast Hold Time . . . . . . . . . 10 nanoseconds Fast Negation Period . . . . . . 30 nanoseconds ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ 4.7.1. Arbitration Delay  The minimum time an SCSI device shall wait from asserting BSY for arbitration until the DATA BUS can be examined to see if arbitration has been won. There is no maximum time. 4.7.2. Assertion Period  The minimum time that a target shall assert REQ (or REQB) while using synchronous data transfers. Also, the minimum time that an initiator shall assert ACK (or ACKB) while using synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. 4.7.3. Bus Clear Delay  The maximum time for an SCSI device to stop driving all bus signals after: (1) The BUS FREE phase is detected (BSY and SEL both false for a bus settle delay) (2) SEL is received from another SCSI device during the ARBITRATION phase (3) The transition of RST to true. NOTE: For the first condition above, the maximum time for an SCSI device to clear the bus is 1200 nanoseconds from BSY and SEL first becoming both false. If an SCSI device requires more than a bus settle delay to detect BUS FREE phase, it shall clear the bus within a bus clear delay minus the excess time. 4.7.4. Bus Free Delay  The minimum time that an SCSI device shall wait from its detection of the BUS FREE phase (BSY and SEL both false for a bus settle delay) until its assertion of BSY when going to the ARBITRATION phase. 4.7.5. Bus Set Delay  The maximum time for an SCSI device to assert BSY and its SCSI ID bit on the DATA BUS after it detects BUS FREE phase (BSY and SEL both false for a bus settle delay) for the purpose of entering the ARBITRATION phase. 4.7.6. Bus Settle Delay  The time to wait for the bus to settle after changing certain control signals as called out in the protocol definitions. 4.7.7. Cable Skew Delay  The maximum difference in propagation time allowed between any two SCSI bus signals when measured between any two SCSI devices. 4.7.8. Data Release Delay  The maximum time for an initiator to release the DATA BUS signals following the transition of the I/O signal from false to true. 4.7.9. Deskew Delay  The minimum time required for deskew of certain signals. 4.7.10. Disconnection Delay  The minimum time that a target shall wait after releasing BSY before participating in an ARBITRATION phase when honoring a DISCONNECT message from the initiator. 4.7.11. Hold Time  The minimum time added between the assertion of REQ (or REQB) or ACK (or ACKB) and the changing of the data lines to provide hold time in the initiator or target, respectively, while using synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. 4.7.12. Negation Period  The minimum time that a target shall negate REQ (or REQB) while using synchronous data transfers. Also, the minimum time that an initiator shall negate ACK (or ACKB) while using synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. 4.7.13. Power-On to Selection Time  The recommended maximum time from power application until an SCSI target is able to respond with appropriate status and sense data to the TEST UNIT READY, INQUIRY, and REQUEST SENSE commands. 4.7.14. Reset to Selection Time  The recommended maximum time after a hard RESET condition until an SCSI target is able to respond with appropriate status and sense data to the TEST UNIT READY, INQUIRY, and REQUEST SENSE commands. 4.7.15. Reset Hold Time  The minimum time for which RST is asserted. There is no maximum time. 4.7.16. Selection Abort Time  The maximum time that a target (or initiator) shall take from its most recent detection of being selected (or reselected) until asserting a BSY response. This time-out is required to ensure that a target (or initiator) does not assert BSY after a SELECTION (or RESELECTION) phase has been aborted. This is not the selection time-out period; see 5.1.3.1 and 5.1.4.2 for a complete description. 4.7.17. Selection Time-out Delay  The minimum time that an initiator (or target) should wait for a BSY response during the SELECTION (or RESELECTION) phase before starting the time- out procedure. Note that this is only a recommended time period. The specifications for the peripheral devices shall be consulted for the actual timing requirements. 4.7.18. Transfer Period  The Transfer Period specifies the minimum time allowed between the leading edges of successive REQ pulses and of successive ACK pulses while using synchronous data transfers. (See 5.1.5.2 and 5.6.21.) 4.8. Fast Synchronous Transfer Option When devices negotiate a synchronous data transfer period between 100 ns and 200 ns they are said to be using "fast synchronous data transfers". Devices which negotiate a synchronous data transfer period greater than 200 ns use timing parameters specified in 4.7. When a fast synchronous data transfer period is negotiated, those specific times redefined in this section are used; those not redefined remain the same. The minimum synchronous data transfer period is 100 ns. 4.8.1. Fast Assertion Period  This value is the minimum time that a target shall assert REQ (or REQB) while using fast synchronous data transfers. Also, the minimum time that an initiator shall assert ACK (or ACKB) while using fast synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. 4.8.2. Fast Cable Skew Delay  This value is the maximum difference in propagation time allowed between any two SCSI bus signals when measured between any two SCSI devices while using fast synchronous data transfers. 4.8.3. Fast Deskew Delay  This value is the minimum time required for deskew of certain signals while using fast synchronous data transfers. 4.8.4. Fast Hold Time  This value is the minimum time added between the assertion of REQ (or REQB) or ACK (or ACKB) and the changing of the data lines to provide hold time in the initiator or target, respectively, while using fast synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. 4.8.5. Fast Negation Period  This value is the minimum time that a target shall negate REQ (or REQB) while using fast synchronous data transfers. Also, the minimum time that an initiator shall negate ACK (or ACKB) while using fast synchronous data transfers. REQB and ACKB timings only apply to optional wide data transfers. Section 5 changes recommened to implement a single 68 pin connector 5.1.2. ARBITRATION Phase The ARBITRATION phase allows one SCSI device to gain control of the SCSI bus so that it can assume the role of an initiator or target. The procedure for an SCSI device to obtain control of the SCSI bus is as follows: (1) The SCSI device shall first wait for the BUS FREE phase to occur. The BUS FREE phase is detected whenever both the BSY and SEL signals are simultaneously and continuously false for a minimum of a bus settle delay. IMPLEMENTORS NOTE: This bus settle delay is necessary because a transmission line phenomenon known as a "wire-OR glitch" may cause the BSY signal to briefly appear false, even though it is being driven true. (2) The SCSI device shall wait a minimum of a bus free delay after detection of the BUS FREE phase (i.e. after the BSY and SEL signals are both false for a bus settle delay) before driving any signal. (3) Following the bus free delay in Step (2), the SCSI device may arbitrate for the SCSI bus by asserting both the BSY signal and its own SCSI ID, however the SCSI device shall not arbitrate (i.e. assert the BSY signal and its SCSI ID) if more than a bus set delay has passed since the BUS FREE phase was last observed. IMPLEMENTORS NOTE: There is no maximum delay before asserting the BSY signal and the SCSI ID following the bus free delay in Step (2) as long as the bus remains in the BUS FREE phase. However, SCSI devices that delay longer than a bus settle delay plus a bus set delay from the time when the BSY and SEL signals first become false may fail to participate in arbitration when competing with faster SCSI devices. (4) After waiting at least an arbitration delay (measured from its assertion of the BSY signal) the SCSI device shall examine the DATA BUS. If a higher priority SCSI ID bit is true on the DATA BUS (DB(7) is the highest) , then the SCSI device has lost the arbitration and the SCSI device may release its signals and return to Step (1). If no higher priority SCSI ID bit is true on the DATA BUS, then the SCSI device has won the arbitration and it shall assert the SEL signal. Any other SCSI device that is participating in the ARBITRATION phase has lost the arbitration and shall release the BSY signal and its SCSI ID bit within a bus clear delay after the SEL signal becomes true. An SCSI device | that loses arbitration may return to Step (1). The SCSI ID | priority is shown below: | Priority | Highest --> Lowest | | A Cable SCSI ID=7 SCSI ID=0 | A/B Cable SCSI ID=7 SCSI ID=0 | W Cable SCSI ID=7 SCSI ID=0 SCSI ID=15 SCSI ID=8 (5) The SCSI device that wins arbitration shall wait at least a bus clear delay plus a bus settle delay after asserting the SEL signal before changing any signals. NOTE: The SCSI ID bit is a single bit on the DATA BUS that corresponds to the SCSI device's unique SCSI address. All other | DATA BUS bits shall be released by the SCSI device. Parity is not valid during the ARBITRATION phase. During the ARBITRATION | phase, DB(P) or DB(P1) may be released or asserted, but shall not be actively driven false. 5.1.5.3. Wide Data Transfer Wide data transfer is optional and may be used in the DATA phase only if a nonzero wide data transfer agreement is in effect (see WIDE DATA TRANSFER REQUEST message, 5.6.23). The messages determine the use of wide mode by both SCSI devices and establish a data path width to be used during the DATA phase. Wide data transfers of 16- or 32-bits may be established. Although not mandatory, it is recommended that targets and initiators that support 32-bit wide transfers also support 16-bit wide transfers as well. All SCSI devices shall support 8-bit data transfers. During 16-bit wide data transfers, the first logical data byte for each data phase shall be transferred across the DB(7-0,P) signals on the A cable and the second logical data byte shall be | transferred across the DB(15-8,P1) signals on the B cable or the W | cable. Subsequent pairs of data bytes are likewise transferred in | parallel across the A and B cables (see Figure 5-1) or the W | cable. During 32-bit wide data transfers, the first logical data byte for each data phase shall be transferred across the DB(7-0,P) signals on the A cable and the second, third, and fourth logical data bytes shall be transferred across the DB(15-8,P1), DB(23-16,P2), and DB(31-24,P3) signals, respectively, on the B cable. Subsequent groups of four data bytes are likewise transferred in parallel across the A and B cables (see Figure 5-1). When transferring bytes W, X, Y and Z across the three bus widths, they are transferred as shown below: Hand- 8-bit 16-bit 32-bit shake W Cable ______ ______ # A Cable B Cable A Cable / B Cable \ A Cable ÚÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄ¿ 1 ³ W ³ ³ X ³ W ³ ³ Z ³ Y ³ X ³ W ³ ÃÄÄÄÄÄÄÄ´ ÃÄÄÄÄÄÄijÄÄÄÄÄÄÄ´ ÃÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ 2 ³ X ³ ³ Z ³ Y ³ 31...24 23...16 15....8 7.....0 ÃÄÄÄÄÄÄÄ´ ÃÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ 3 ³ Y ³ 15....8 7.....0 Bit Number ÃÄÄÄÄÄÄÄ´ 4 ³ Z ³ Bit Number ÃÄÄÄÄÄÄÄ´ 7.....0 Bit Number NOTE: This figure does not represent how these bytes are stored in the initiator's memory, which may be different. Figure 5-1: Wide SCSI Byte Ordering If the last data byte transferred for a command does not fall on the DB(15- 8,P1) signals for a 16-bit wide transfer or the DB(31-24,P3) signals for a 32- bit wide transfer, then the values of the remaining higher-numbered bits are undefined. However, parity bits for these undefined bytes shall be valid for whatever data is placed on the bus. To ensure proper data integrity, certain sequence requirements | shall be met between the REQ/ACK handshakes on the A cable and | the W cable, and the REQB/ACKB handshakes on the B cable: (1) The REQB and ACKB signals shall only be asserted during data phases while a nonzero wide data transfer agreement is in | effect on a B cable system. These signals shall not be asserted during other phases. (2) The same information transfer mode (asynchronous or synchronous) shall be used for both the A cable and the B cable. If synchronous data transfer mode is in effect, the same REQ/ACK offset and transfer period shall be used for both cables. (3) The information transfer procedures defined in 5.1.5.1 and 5.1.5.2 for the A cable (the REQ, ACK, and DB(7-0,P) signals) and | the W cable (the REQ, ACK, DB(15-8,P1) signals) shall also apply to the B cable (the REQB, ACKB, and DB(31-8,P1,P2,P3) signals). The only means available for a target to manage the timing relationship between the signals on the two cables is its management of the REQ and REQB signals. Similarly, the only means for the initiator to manage the timing between the two cables is its management of the ACK and ACKB signals. (4) The target shall ensure that the number of REQ/ACK handshakes and the number of REQB/ACKB handshakes in a data phase are equal before it changes to another phase. The target shall not change the phase until the ACK and ACKB signals have both become false for the last REQ/ACK handshake and the last REQB/ACKB handshake. IMPLEMENTORS NOTE: If any violations of these rules are detected by the target, the target may attempt to end the data phase and return CHECK CONDITION status. If it is impossible to correctly terminate the data phase, the target may abnormally terminate the connection by releasing the BSY signal and entering the BUS FREE phase unexpectedly. If any violations of these rules are detected by the initiator, the initiator may attempt to send an INITIATOR DETECTED ERROR message to the target. If the initiator is unable to terminate the connection normally, it may generate the reset condition to terminate the I/O process. Section 7 changes recommened to implement a single 68 pin connector 7.2.3.3. COPY Function Code 00h and 01h The format for the segment descriptors for COPY transfers between direct- access and sequential-access devices is specified in Table 7-8. This format is required for COPY function codes 00h or 01h. The segment descriptor may be repeated up to 256 times within the parameter list length specified in the command descriptor block. Table 7-8: Segment Descriptor for COPY Function Codes 00h and 01h ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Source Address |Reserved| Cat | Source LUN | -----|-----------------------------------------------------------------------| |1 | Destination Address | Hidest | Hisour | Destination LUN | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- Sequential-Access Device Block Length ---| 3 | (LSB) | -----|-----------------------------------------------------------------------| 4 | (MSB) | - - -|- - Direct-Access Device Number of Blocks - -| 7 | (LSB) | -----|-----------------------------------------------------------------------| 8 | (MSB) | - - -|- - Direct-Access Device Logical Block Address - -| 11 | (LSB) | ============================================================================== The source address and source LUN fields specify the SCSI bus ID and logical unit of the device to copy the data from for this segment of the COPY command. The destination address and destination LUN fields specify the SCSI bus ID and logical unit to copy the data to for this segment of the COPY command. Some SCSI devices may not support third-party COPY in which the copying SCSI device is not the source or destination device. Some SCSI devices only support COPY within the SCSI device and not to other SCSI devices. If an unsupported COPY operation is requested, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST with an additional sense code of INVALID FIELD IN PARAMETER LIST (see 7.2.3.1). A catenate (Cat) bit (optional) of one indicates that the COPY manager shall catenate the last source block of a segment with the first source block of the next segment if the last source block does not end exactly at the end of the destination block. The definition of a cat bit of zero depends on the setting of the pad bit in the command descriptor block (see 7.2.3.7). The sequential-access device block-length field specifies the block length to be used on the sequential-access logical unit during this segment of the COPY command. If the SCSI device managing the COPY knows this block length is not supported, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST with an additional sense code of INVALID FIELD IN PARAMETER LIST . If the block length is found to be invalid while executing a read or write operation to the sequential-access device, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to COPY ABORTED (see 7.2.3.2). | The high destination address (Hidest) bit is the most significant | bit of the destination address field. | The high source address (Hisour) bit is the most significant bit | of the source address field. The direct-access device number of blocks field specifies the number of blocks in the current segment to be copied. A value of zero indicates that no blocks shall be transferred in this segment. The direct-access device logical block address field specifies the starting logical block address on the logical unit for this segment. 7.2.3.4. COPY Function Code 02h The format for the segment descriptors for COPY transfers among direct- access devices is specified in Table 7-9. This format is required for COPY function code 02h. The segment descriptor may be repeated up to 256 times within the parameter list length specified in the command descriptor block. Table 7-9: Segment Descriptor for COPY Function Code 02h ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Source Address | DC | Cat | Source LUN | -----|-----------------------------------------------------------------------| |1 | Destination Address | Hidest | Hisour | Destination LUN | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | (MSB) | - - -|- - Number of Blocks - -| 7 | (LSB) | -----|-----------------------------------------------------------------------| 8 | (MSB) | - - -|- - Source Logical Block Address - -| 11 | (LSB) | -----|-----------------------------------------------------------------------| 12 | (MSB) | - - -|- - Destination Logical Block Address - -| 15 | (LSB) | ============================================================================== See 7.2.3.3 for definitions of the source address, the source LUN, | the destination address, the destination LUN, the Hidest, the Hisour, and CAT fields. A destination count (DC) bit of zero indicates that the number of blocks field refers to the source logical unit. A DC bit of one indicates that the number of blocks field refers to the destination logical unit. The number of blocks field specifies the number of blocks to be transferred to or from (depending on the DC bit) the device during this segment. A value of zero indicates that no blocks shall be transferred. The source logical block address field specifies the starting logical block address on the source device. The destination logical block address field specifies the starting logical block address on the destination device. 7.2.3.5. COPY Function Code 03h The format for the segment descriptors for COPY transfers among sequential- access devices is specified by Table 7-10. This format is required for COPY function code 03h. The segment descriptor may be repeated up to 256 times within the parameter list length specified in the command descriptor block. Table 7-10: Segment Descriptor for COPY Function Code 03h ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Source Address | DC | Cat | Source LUN | -----|-----------------------------------------------------------------------| |1 | Destination Address | Hidest | Hisour | Destination LUN | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | (MSB) | -----|--- Source Block Length ---| 5 | (LSB) | -----|-----------------------------------------------------------------------| 6 | (MSB) | -----|--- Destination Block Length ---| 7 | (LSB) | -----|-----------------------------------------------------------------------| 8 | (MSB) | - - -|- - Number of Blocks - -| 11 | (LSB) | ============================================================================== See 7.2.3.3 for definitions of the source address, the source LUN, | the destination address, the destination LUN, the Hidest, the | Hisour,and CAT fields. A destination count (DC) bit of zero indicates that the number of blocks field refers to the source logical unit. A DC bit of one indicates that the number of blocks field refers to the destination logical unit. The source block length field specifies the block-length of the source device for this segment of the COPY. A zero in this field indicates variable block-length. For non-zero values, this field shall match the logical unit's actual block-length. If block-length mismatches are detected by the SCSI device managing the COPY, the command shall be terminated with CHECK CONDITION status. The sense key shall be set to ILLEGAL REQUEST and the additional sense code shall be set to INVALID FIELD IN PARAMETER LIST (see 7.2.3.1). If the mismatches are detected during the read operation by the COPY manager, the command shall be terminated with CHECK CONDITION status. The sense key shall be set to COPY ABORTED (see 7.2.3.2). and the additional sense code shall be set to INVALID FIELD IN PARAMETER LIST. The destination block-length field specifies the block length to be used on the destination logical unit during the COPY. Destination block length mismatches are handled in the same manner as source block length mismatches. The number of blocks field specifies the number of blocks to be transferred to or from (depending on the DC bit) the device during this segment. A value of zero indicates that no blocks shall be transferred. 7.2.3.6. COPY Function Code 04h The format for the segment descriptors for image COPY transfers between sequential-access devices is specified in Table 7-11. This format is required for COPY function code 04h. The segment descriptor may be repeated up to 256 times within the parameter list length specified in the command descriptor block. Table 7-11: Segment Descriptor for COPY Function Code 04h ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Source Address | Reserved | Source LUN | -----|-----------------------------------------------------------------------| |1 | Destination Address | Hidest | Hisour | Destination LUN | -----|-----------------------------------------------------------------------| 2 | Count | -----|-----------------------------------------------------------------------| 3 | | - - -|- - Reserved - -| 7 | | -----|-----------------------------------------------------------------------| 8 | | - - -|- - Vendor Specific - -| 11 | | ============================================================================== See 7.2.3.3 for definitions of the source address, the source LUN, | the destination address, the destination LUN, the Hidest, the | Hisour, and CAT fields. The image mode COPY command copies an exact image of the source device medium to the destination device medium, beginning at their current positions. The copy function terminates when the source device: (1) encounters an end-of-partition as defined by the source device (2) encounters an end-of-data as defined by the source device (i.e., BLANK CHECK sense key) (3) has copied the number of consecutive filemarks specified in the count field from the source device to the destination device (4) has copied the number of consecutive setmarks specified in the count field from the source device to the destination device, if the RSmk bit in the device configuration page (see 9.3.3.1) is one. A count field of zero indicates that the COPY command shall not terminate due to any number of consecutive filemarks or setmarks. Other error or exception conditions (e.g., early-warning end-of-partition on the destination device) may cause the COPY command to terminate prior to completion. In such cases, it is not possible to calculate a residue, so the information field in the sense data shall be set to zero. Section 8 changes recommened to implement a single 68 pin connector 8.2. Commands for Direct-Access Devices. The commands for direct-access devices shall be as shown in Tables 8-1 and 8-2. Table 8-1: Commands for Direct-Access Devices(1) ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Operation Command Name Code Type Section ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ CHANGE DEFINITION 40h O 7.2.1 COMPARE 39h O 7.2.2 COPY 18h O 7.2.3 COPY AND VERIFY 3Ah O 7.2.4 FORMAT UNIT 04h M 8.2.1 INQUIRY 12h M 7.2.5 LOCK/UNLOCK CACHE 36h O 8.2.2 LOG SELECT 4Ch O 7.2.6 LOG SENSE 4Dh O 7.2.7 MODE SELECT(6) 15h O 7.2.8 MODE SELECT(10) 55h O 7.2.9 MODE SENSE(6) 1Ah O 7.2.10 MODE SENSE(10) 5Ah O 7.2.11 PRE-FETCH 34h O 8.2.3 PREVENT/ALLOW MEDIUM REMOVAL 1Eh O 8.2.4 READ(6) 08h M 8.2.5 READ(10) 28h M 8.2.6 READ BUFFER 3Ch O 7.2.12 READ CAPACITY 25h M 8.2.7 READ DEFECT DATA 37h O 8.2.8 READ LONG 3Eh O 8.2.9 REASSIGN BLOCKS 07h O 8.2.10 RECEIVE DIAGNOSTIC RESULTS 1Ch O 7.2.13 RELEASE(6) 17h M 8.2.11 |RELEASE(10) 57h M 8.2.11 REQUEST SENSE 03h M 7.2.14 RESERVE(6) 16h M 8.2.12 |RESERVE(10) 56h M 8.2.12 REZERO UNIT 01h O 8.2.13 ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Key: M = Command implementation is mandatory. O = Command implementation is optional. Table 8-2: Commands for Direct-Access Devices(2) ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Operation Command Name Code Type Section ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ SEARCH DATA EQUAL 31h O 8.2.14.1 SEARCH DATA HIGH 30h O 8.2.14.2 SEARCH DATA LOW 32h O 8.2.14.3 SEEK(6) 0Bh O 8.2.15 SEEK(10) 2Bh O 8.2.15 SEND DIAGNOSTIC 1Dh M 7.2.15 SET LIMITS 33h O 8.2.16 START STOP UNIT 1Bh O 8.2.17 SYNCHRONIZE CACHE 35h O 8.2.18 TEST UNIT READY 00h M 7.2.16 VERIFY 2Fh O 8.2.19 WRITE(6) 0Ah M 8.2.20 WRITE(10) 2Ah M 8.2.21 WRITE AND VERIFY 2Eh O 8.2.22 WRITE BUFFER 3Bh O 7.2.17 WRITE LONG 3Fh O 8.2.23 WRITE SAME 41h O 8.2.24 ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Key: M = Command implementation is mandatory. O = Command implementation is optional. The following operation codes are vendor-specific: 02h, 05h, 06h, 09h, 0Ch, 0Dh, 0Eh, 0Fh, 10h, 11h, 13h, 14h, 19h, 20h, 21h, 22h, 23h, 24h, 26h, 27h, 29h, 2Ch, 2Dh and C0h through FFh. All remaining operation codes are reserved for future standardization. 8.2.11. RELEASE(6) and RELEASE(10) Commands Peripheral Device Type: Direct-Access, Write-Once, Optical-Memory Operation Code Type: Mandatory Table 8-23: RELEASE(6) Command ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Bit³ 7 ³ 6 ³ 5 ³ 4 ³ 3 ³ 2 ³ 1 ³ 0 ³ Byte ³ ³ ³ ³ ³ ³ ³ ³ ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ 0 ³ Operation Code (17h) ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄ´ 1 ³ Logical Unit Number ³ 3rdPty ³ Third Party Device ID ³ Extent ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄ´ 2 ³ Reservation Identification ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 3 ³ Reserved ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 4 ³ Reserved ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 5 ³ Control Byte ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Table 8-23: RELEASE(10) Command | |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Bit³ 7 ³ 6 ³ 5 ³ 4 ³ 3 ³ 2 ³ 1 ³ 0 ³ Byte ³ ³ ³ ³ ³ ³ ³ ³ ³ |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ |0 ³ Operation Code (57h) ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄ´ |1 ³ Logical Unit Number ³ 3rdPty ³ Reserved ³ Extent ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄ´ |2 ³ Reservation Identification ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |3 ³ Reserved ³ Third Party Device ID ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |4 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |5 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |6 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |7 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |8 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |9 ³ Control Byte ³ |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ The RESERVE and RELEASE commands provide the basic mechanism for contention resolution in multiple-initiator systems. The RELEASE command (Table 8-23) is used to release a previously reserved logical unit, or, if the extent release option is implemented, to release previously reserved extents within a logical unit. It is not an error for an initiator to attempt to release a reservation that is not currently valid. In this case, the target returns GOOD status without altering any other reservation. IMPLEMENTORS NOTE: The reservation queuing option in X3.131-1986 has been removed from SCSI-2. 8.2.11.1. Logical Unit Release (Mandatory) If the extent bit is zero, this command shall cause the target to terminate all logical unit and extent reservations that are active from the initiator to the specified logical unit. The reservation ID field in the command descriptor block is ignored by the target. 8.2.11.2. Extent Release (Optional) If the extent bit is one and the extent release option is not implemented, then the RELEASE command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. This option shall be implemented if the extent reservation option (see 8.2.12.2) is implemented. If the extent bit is one and the extent release option is implemented, this command shall cause any reservation from the requesting initiator with a matching reservation identification to be terminated. Other reservations from the requesting initiator shall remain in effect. 8.2.11.3. Third-Party Release (Mandatory) Third-party release allows an initiator to release a logical unit or extents within a logical unit that were previously reserved using third-party reservation (see 8.2.12.3). Third-party release shall be implemented and is intended for use in multiple-initiator systems that use the COPY command. If the third-party (3rdPty) bit is zero, then a third-party release is not requested. If the 3rdPty bit is one then the target shall release the specified logical unit or extents, but only if the reservation was made using a third-party reservation by the initiator that is requesting the release for the same SCSI device as specified in the third-party device ID field. If the 3rdPty bit is one the target shall not modify the mode parameters for commands received from the third-party device even if the target implements the transfer of mode parameters with a third-party RESERVE command. IMPLEMENTORS NOTE: If a target implements independent storage of mode parameters for each initiator, a third-party RESERVE command copies the current mode parameters for the initiator that sent the RESERVE command to the current mode parameters for the initiator specified as the third-party device (usually a copy master device). The target creates a unit attention condition to notify the third-party device of changed mode parameters due to the reservation. A successful third-party RELEASE command does not return the third-party devices' current mode parameters back to their previous values. The third-party device can issue MODE SENSE and MODE SELECT commands to query and modify the mode parameters. 8.2.12. RESERVE(6) and RESERVE(10) Commands Peripheral Device Type: Direct-Access, Write-Once, Optical-Memory Operation Code Type: Mandatory Table 8-24: RESERVE(6) Command ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Bit³ 7 ³ 6 ³ 5 ³ 4 ³ 3 ³ 2 ³ 1 ³ 0 ³ Byte ³ ³ ³ ³ ³ ³ ³ ³ ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ 0 ³ Operation Code (16h) ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄ´ 1 ³ Logical Unit Number ³ 3rdPty ³ Third Party Device ID ³ Extent ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄ´ 2 ³ Reservation Identification ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 3 ³ (MSB) ³ ÄÄÄÄÄÅÄÄÄ Extent List Length ÄÄÄ´ 4 ³ (LSB) ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 5 ³ Control Byte ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Table 8-24: RESERVE(10) Command | |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ | Bit³ 7 ³ 6 ³ 5 ³ 4 ³ 3 ³ 2 ³ 1 ³ 0 ³ Byte ³ ³ ³ ³ ³ ³ ³ ³ ³ |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ |0 ³ Operation Code (16h) ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄ´ |1 ³ Logical Unit Number ³ 3rdPty ³ Reserved ³ Extent ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄ´ |2 ³ Reservation Identification ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |3 ³ Reserved ³ Third Party Device ID ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |4 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |5 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |6 ³ Reserved ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |7 ³ (MSB) ³ |ÄÄÄÄÅÄÄÄ Extent List Length ÄÄÄ´ |8 ³ (LSB) ³ |ÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ |9 ³ Control Byte ³ |ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ The RESERVE and RELEASE commands provide the basic mechanism for contention resolution in multiple-initiator systems. The RESERVE command (Table 8-24) is used to reserve a logical unit or, if the extent reservation option is implemented, extents within a logical unit. The third-party reservation allows logical units or extents to be reserved for another specified SCSI device. IMPLEMENTORS NOTE: The reservation queuing option in X3.131-1986 has been removed from SCSI-2. 8.2.12.1. Logical Unit Reservation (Mandatory). If the extent bit is zero, this command shall request that the entire logical unit be reserved for the exclusive use of the initiator until the reservation is superseded by another valid RESERVE command from the initiator that made the reservation or until released by a RELEASE command from the same initiator that made the reservation, by a BUS DEVICE RESET message from any initiator, by a hard RESET condition, or by a power on cycle. A logical unit reservation shall not be granted if the logical unit or any extent is reserved by another initiator. It shall be permissible for an initiator to reserve a logical unit that is currently reserved by that initiator. If the extent bit is zero, the reservation identification and the extent list length shall be ignored. If the logical unit, or any extent within the logical unit is reserved for another initiator, the target shall return RESERVATION CONFLICT status. If, after honoring the reservation, any other initiator then subsequently attempts to perform any command on the reserved logical unit other than an INQUIRY command, a REQUEST SENSE command, or a RELEASE command, which shall be ignored, then the command shall be rejected with RESERVATION CONFLICT status. 8.2.12.2. Extent Reservation (Optional) The reservation identification field provides a means for an initiator to identify each extent reservation. This allows an initiator in a multiple tasking environment, to have multiple reservations outstanding. The reservation identification is used in the RELEASE command to specify which reservation is to be released. It is also used in superseding RESERVE commands to specify which reservation is to be superseded. If the extent reservation option is implemented, then the extent release option (see 8.2.11.2) shall also be implemented. These options permit multiple extents within the logical unit to be reserved, each with a separate reservation type. If the extent bit is one, and the extent reservation option is implemented, then the target shall process the reservation request as follows: (1) The extent list shall be checked for the number of extents in the reservation request. If the extent list length is zero, no current reservations shall be changed, no new reservations shall be created, and this condition shall not be treated as an error. If the extent list contains more extents than are supported on the logical unit, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. If the extent list contains more extents than are currently available on the logical unit, then the target shall return a RESERVATION CONFLICT status. (2) The extent list shall be checked for valid extent logical block addresses. If any logical block address is invalid for this logical unit, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. The extent list shall be checked for invalid extent overlaps (as defined by reservation type) with other extent descriptors in the extent list and if invalid overlaps are found, the command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. (3) If the requested reservation does not conflict with an existing reservation, the extents specified shall be reserved until superseded by another valid RESERVE command from the initiator that made the reservation or until released by a RELEASE command from the same initiator, by a BUS DEVICE RESET message from any initiator, or by a hard RESET condition. If either of the last two conditions occur, the next command from each initiator shall be terminated with CHECK CONDITION status and the sense key shall be set to UNIT ATTENTION. (4) If the reservation request conflicts with an existing reservation, then the target shall return a RESERVATION CONFLICT status. If the extent bit is one, and the extent reservation option is not implemented, then the RESERVE command shall be rejected with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. Table 8-25: Data Format of Extent Descriptors ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ Bit³ 7 ³ 6 ³ 5 ³ 4 ³ 3 ³ 2 ³ 1 ³ 0 ³ Byte ³ ³ ³ ³ ³ ³ ³ ³ ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ 0 ³ Control Byte ³ RelAdr ³ Reservation Type³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 1 ³ (MSB) ³ - - -ÃÄ - Number of Blocks - -³ 3 ³ (LSB) ³ ÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ 4 ³ (MSB) ³ - - -ÃÄ - Logical Block Address - -³ 7 ³ (LSB) ³ ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ The size of the extent list shall be defined by the extent list length parameter. The extent list shall consist of zero or more descriptors as shown in Table 8-25. Each extent descriptor defines an extent beginning at the specified logical block address for the specified number of blocks. If the number of blocks is zero, the extent shall begin at the specified logical block address and continue through the last logical block address on the logical unit. The reservation type field shall determine the type of reservation to be effected for each extent. Four types of reservations are possible as follows: DB(1) DB(0) Reservation Type ÄÄÄÄÄ ÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ 1 0 Read Exclusive 0 1 Write Exclusive 1 1 Exclusive Access 0 0 Read Shared Read Exclusive. While this reservation is active, no other initiator shall be permitted read operations to the indicated extent. This reservation shall not inhibit write operations from any initiator or conflict with a write exclusive reservation; however, read exclusive, exclusive access, and read shared reservations that overlap this extent shall conflict with this reservation. Write Exclusive. While this reservation is active, no other initiator shall be permitted write operations to the indicated extent. This reservation shall not inhibit read operations from any initiator or conflict with a read exclusive reservation from any initiator. This reservation shall conflict with write exclusive, exclusive access, and read shared reservations that overlap this extent. Exclusive Access. While this reservation is active, no other initiator shall be permitted any access to the indicated extent. All reservation types that overlap this extent shall conflict with this reservation. Read Shared. While this reservation is active, no write operations shall be permitted by any initiator to the indicated extent. This reservation shall not inhibit read operations from any initiator or conflict with a read shared reservation. Read exclusive, write exclusive, and exclusive access reservations that overlap with this extent shall conflict with this reservation. If the relative address bit is one, the logical block address in the extent descriptor shall be treated as a two's complement displacement. This displacement shall be added to the logical block address last accessed on the logical unit to form the logical block address for this extent. This feature is only available when linking commands and requires that a previous command in the linked group has accessed a logical block on the logical unit; if not, the RESERVE command shall be terminated with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. If an initiator attempts a command to a logical block that has been reserved and that access is prohibited by the reservation, the command shall not be performed and the command shall be terminated with a RESERVATION CONFLICT status. If a reservation conflict precludes any part of the command, none of the command shall be performed. COPY commands shall be terminated with CHECK CONDITION status and the sense key shall be set to DATA PROTECT if any part of the copy operation is prohibited by an active reservation. If any extent in a logical unit is reserved in any way, by any initiator, a FORMAT UNIT command shall be rejected with a RESERVATION CONFLICT status. 8.2.12.3. Third Party Reservation (Mandatory). The third-party reservation for the RESERVE command allows an initiator to reserve a logical unit or extents within a logical unit for another SCSI device. This is intended for use in multiple-initiator systems that use the COPY command. Third-party reservation is required. If the third-party (3rdPty) bit is zero, then a third-party reservation is not requested. If the 3rdPty bit is one then the target shall reserve the specified logical unit or extents for the SCSI device specified in the third- party device ID field. The target shall preserve the reservation until it is superseded by another valid RESERVE command from the initiator that made the reservation or until it is released by the same initiator, by a BUS DEVICE reset message from any initiator, or a hard reset condition. The target shall ignore any attempt to release the reservation made by any other initiator. A 3rdPty bit of one causes any subsequent command issued by the third-party device to be executed according to the mode parameters in effect for the initiator sending the RESERVE command. IMPLEMENTORS NOTE: This transfer of the mode parameters is applicable to target devices which store mode information independently for different initiators. This mechanism allows an initiator to set the mode parameters of a target for the use of a copy master (i.e., the third-party device). The third-party copy master may subsequently issue a MODE SELECT command to modify the mode parameters. 8.2.12.4. Superseding Reservations (Mandatory) An initiator that holds a current reservation (unit or extent) may modify that reservation by issuing another RESERVE command (unit or extent) to the same logical unit. The superseding RESERVE command shall release the previous reservation state (unit or extent) when the new reservation request is granted. If the superseding reservation is for an extent reservation and the current reservation is also an extent reservation, the current extent reservation identification value is used for the superseding reservation. The current reservation shall not be modified if the superseding reservation request cannot be granted. If the superseding reservation cannot be granted because of conflicts with a previous reservation (other than the reservation being superseded), then the target shall return RESERVATION CONFLICT status. IMPLEMENTORS NOTE: Superseding reservations allow the SCSI device ID to be changed on a reservation using the third-party reservation option. This capability is necessary for certain situations when using COMPARE, COPY, and COPY AND VERIFY commands.