X3T9.2/88-059 Rev 1 May 27, 1988 To: X3T9.2 Membership From: John B. Lohmeyer, X3T9.2 Chairman Subject: SDTR Wording revisited (again and again) (and again) Peter Johansson gave Bill Spence some wording enhancements which he recommended in place of the first two sentences of the first paragraph of 5.5.3.3. Bill Spence dutifully place Peter's proposal on the SCSI BBS along with his recommendation that the enhancement wasn't worth doing. (I think Bill is tiring of clarifying SDTR.) I thought Peter's idea was worth pursuing with a couple further changes, so I placed my proposal on the SCSI BBS and took it to the May working group meeting. The working group asked me to make a few additional changes and to place the resulting wording in a proposal. This is it. (I now know why Bill is tiring of this.) Revision 1: The ink had barely dried on Revision 0, when Bill Spence called me to say that my proposal left out the notion that a device receiving an SDTR message should be required to respond at that time and not reject the negotiation just because it is inconvenient (which could/should be interpreted to be agreement on asynchronous transfers). Bill must really feel good to have passed this puppy off to me... Anyway, here is my attempt to address Bill's concern (the last sentence is new, the rest is unchanged): " A SYNCHRONOUS DATA TRANSFER REQUEST (SDTR) message exchange shall be initiated by an SCSI device whenever a previously-arranged data transfer agreement may have become invalid. Examples of the agreement becoming invalid are: (1) after a "hard" reset condition (2) after a BUS DEVICE RESET message (3) after a power cycle and (4) after any condition which may leave the data transfer agreement in an indeterminate state. In addition, an SCSI device may initiate an SDTR message exchange whenever it is appropriate to negotiate a new data transfer agreement (either synchronous or asynchronous). SCSI devices that are capable of synchronous data transfers shall not respond to an SDTR message with a MESSAGE REJECT message. " The above wording would still replace the first 2 sentences of the first paragraph of 5.5.3.3.