Multi-command download proposal

Gerry Houlder (Notes) Gerry_Houlder at notes.seagate.com
Fri Apr 22 17:08:15 PDT 1994


I have two problems with the multi-command download proposal sent out by Ken
Cummings.
 
1) He has included wording that requires the last command in a sequence to have
a zero value for transfer length. This is undesireable. At all other times for
this command, a zero length means that the target should transfer zero bytes.
This meaning should be retained! The initiator should always indicate the
correct number of bytes to be transferred in the transfer length field.
     The target will know that all bytes have been transferred by noticing that
the Buffer Offset + Parameter List Length for a command adds up to the maximum
number of bytes that the target is expecting. If this isn't good enough, we
could define a particular Buffer ID value (0xFF ?) for the last piece.
 
2) He includes a requirement that the new firmware doesn't take effect until a
Reset occurs. This requirement is clearly unacceptable for the Download mode
(as opposed to the Download & Save mode) because a reset would revert to the
old firmware again. I prefer having the new firmware always take effect as soon
as GOOD status has been reported for the last WRITE BUFFER command.
     Our implementation uses the time between taking the last data byte and
presenting status (disconnected from the bus, of course) to do integrity
checking of the entire firmware and programming the firmware into flash PROM in
the controller. The GOOD status provides positive indication that everything
has gone well. This implementation doesn't store the firmware on the drive, but
I can understand Jim McGrath's (of Quantum) desire to have one or several
firmware versions stored on the disk drive. The requirements of the standard
must be acceptable to any of these implementations.
--
Gerry Houlder (Notes)  (Gerry_Houlder at notes.seagate.com)
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### OGATE Version 7 message trace and attachment information:
### MsgFileName: m:\mgate\outbound\611.MSG
### Org Date:    04-22-94 11:40:38 AM
### From:        Gerry Houlder at SEAGATE
### To:          scsi @ WichitaKS.NCR.COM @ internet
### Subject:     RE: Multi-command download proposal
### Attachments: none




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