sanjiv@bmers187.uucp (Sanjiv Khurana) (10/17/90)
Mac SCSI Expert Advice Needed
----------------------------
Subject: how to reselect the Mac after disconnection.
The sequence of events on the SCSI bus is:
Mac gets bus
Mac selects device (ATN asserted)
Mac issues IDENTIFY message
Mac issues data transfer command
Device issues "SAVE DATA POINTERS" message
Device issues "DISCONNECT" message
<bus free, so far so good>
Device gets bus
Device attempts to reselect Mac
Mac ignores device completely
The problem is how to make the Mac respond to reselection. I can poll the
SCSI bus (using SCSIStat) but once I recognize that the device wants
to reselect, how do I tell the Mac that I want to acknowledge the
reselection? I need to assert the BSY line to acknowledge it, according
to the SCSI standard. Once that's done, the device will take over again, and
all's well.
I am working on a Mac II with the old SCSI manager and system 6.0.5.
Thanks for any advice...
If possible, please respond via e-mail to "gbrown@bnr.ca" (bitnet)
Gord Browndas@Apple.COM (David Shayer) (10/19/90)
In article <1990Oct17.143151.5125@bmers145.bnr.ca> sanjiv@bmers187.uucp (Sanjiv Khurana) writes: >Mac SCSI Expert Advice Needed >---------------------------- >Subject: how to reselect the Mac after disconnection. > >The problem is how to make the Mac respond to reselection. I can poll the >SCSI bus (using SCSIStat) but once I recognize that the device wants >to reselect, how do I tell the Mac that I want to acknowledge the >reselection? I need to assert the BSY line to acknowledge it, according >to the SCSI standard. Once that's done, the device will take over again, and >all's well. I tried to e-mail you, but our mailer claimed it couldn't reach you, so I'm responding publicly. Unfortunately, disconnect/reconnect is not supported by the Mac SCSI manager. In other words, you're stuck. There is no legal way to do what you want to do. Some third party's have rewritten to SCSI manager to include this feature. But I would not recommend this. David