paulm@ccicpg.UUCP (Paul Moreau) (11/03/90)
Well after some further study I've come up with the following:
I reversed engineered the adpter board and it works very similar to the way
I've heard the adapter in an SH204 works. There is an adpter address decoder
that is hooked to data bits 5-7 of the ACSI bus. The output of this goes
to the PAL which qualifies this with ACSI CS * A1 and some SCSI signals.
An output from the PAL sets -SEL and SCSI D0 together (they are physically
wired together). On the first write to the host adapter #$88, #$ffff8606
does the host adapter and SCSI selection at the same time. Come to think
of it, I'm not 100% sure this is a BMS100. I got the board from a friend
who's drive box (it might of been an SH204) bit the dust. He just upgraded
to a different and larger drive and gave me the adpater.
Anyway, I think I have two choices:
A. I can alter the design to allow different SCSI selections by adding a
1-of-8 decoder chip ala 74LS138 to ACSI bits 0-2 and send the output
tri-stated by a buffer to the SCSI bus lines. This should maintain
compatibility with the disc driver since for selection a zero is on these
three lines anyways. Just setting them to 6 should set SCSI bit 6 and
due to the 1-of-8 get the radial selection bits.
-- or --
B. I can leave the Tape drive at ID 0 and just use another host adapter set
at a different ACSI address.
Currently I am tending to lean towards B (OK, I'm lazey :^) ).
Anyways, what say you guys? A or B. As I said earlier, I'll release the
code to any and all.
The tape drive I am playing with is a Cypher 540 with the Emulex SCSI
'enhancement'. The code has the driver built in and is a klone of the
unix flavor of tar. It will tar in and out complete directory structures
or devices (ie. tar -cv c:) as well as files.
---
.==========================================================.
| ### ####### ### | N O R T H | /==============\ |
| ### ### ### | A M E R I C A |< An STC Company >|
| ### ####### ####### | (was CCI) | \==============/ |
|----------------------------------------------------------|
| UUCP: ..uunet!ccicpg!dl2!paulm | Paul L. Moreau |
| or ..uunet!ccicpg!dl1!paulm | Sr. Diag Software Eng. |
| or ..uunet!ccicpg!paulm | Irvine, California |
`=========================================================='
Nobody wants constructive criticism. It's all we can do to put up with
constructive praise.