X3T9.2/90-166 Rev 1

                                                Date: 10/30/90

John Lohmeyer
Chairman X3T9.2

Subject: Initiator Support of Modify Data Pointers Message



     As a result of discussions of my earlier proposal on 
additional caching control and performance features 
(X3T9.2/90-021), an action item was assigned to Gerry Houlder 
at the last X3T9.2 meeting. That action was to move the bit 
for control of Modify Data pointer Messages to the 
Disconnect/Reconnect Page.

     The attached proposed revision to the 
Disconnect\Reconnect page fulfills the action item. I have 
included a write up for only the additions to the page. The 
balance of the page remains the same.

     The proposal was discussed at the 30 October working 
group meeting and I have included the requested modifications.



                                   G.E. Milligan
                                   Director, Product Strategy


7.3.3.2. Disconnect-Reconnect Page

                    Table 7-68: Disconnect-Reconnect Page

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |   PS   |Reserved|         Page Code (02h)                             |
-----|-----------------------------------------------------------------------|
 1   |                           Page Length (0Eh)                           |
-----|-----------------------------------------------------------------------|
 2   |                           Buffer Full Ratio                           |
-----|-----------------------------------------------------------------------|
 3   |                           Buffer Empty Ratio                          |
-----|-+---------------------------------------------------------------------|
 4   | (MSB)                                                                 |
-----|---                        Bus Inactivity Limit                     ---|
 5   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 6   | (MSB)                                                                 |
-----|---                        Disconnect Time Limit                    ---|
 7   |                                                                 (LSB) |
-----|-+---------------------------------------------------------------------|
 8   | (MSB)                                                                 |
-----|---                        Connect Time Limit                       ---|
 9   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 10  | (MSB)                                                                 |
-----|---                        Maximum Burst Size                       ---|
 11  |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 12  |  EMDP  |                  Reserved                  |      DTDC       |
-----|-----------------------------------------------------------------------|
 13  |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 14  |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 15  |                           Reserved                                    |
==============================================================================

  The Enable Modify Data Pointers (EMDP) bit indicates whether 
or  not the initiator allows the Modify Data Pointers  message 
to  be  sent  by the target. If the EMDP bit is  a  zero,  the 
target shall not issue the Modify Data Pointer message. If the 
EMDP bit is a one, the target is allowed to issue Modify  Data 
Pointer messages. 

  If  the EMDP bit is a one and the initiator  responds  to  a 
Modify Data Pointer message with a Message Reject, then the 
target shall go to the STATUS phase and send the initiator a 
CHECK CONDITION. The sense key shall be set to ABORTED COMMAND 
(0Bh) and the sense code shall be set to INVALID MESSAGE ERROR 
(49h).