[Coco] tc3 scsi controller

[Gene Heskett]

On Thursday 23 October 2014 20:02:56 Jim Hickle did opine
And Gene did reply:
> On 10/18/2014 3:36 AM, Gene Heskett wrote:
> > Nope,only 3 more allowed, the controller itself is one bus address in
> > the scsi scheme of things. scsi bus device addresses are a single set
> > bit, walking across the byte-wide bus. The controller itself is
> > normally at $80. Drive 0 is actually $01, drive 1 is $02, next is
> > $04, $08, $10, $20, $40. Cheers, Gene Heskett
> 
> Unlike most every other controller, the TC^3 doesn't take an ID.

Huh?  That is one of the best features of scsi.  The controller can issue 
a command & go away, or issue another command to another drive, and when 
its done, the device then sends a msg back to the controller.  How can it 
do that if the controller doesn't have an address? 

In all the other scsi controllers I have ever worked with, and that is 
quite a few, the controller has always been device 7 on the bus, at $80 
for its address.  In scsi-ii, the bus address is a single set bit walking 
across the address byte, so drive 0=$01, drive 1=$02, drive 3=$04, to 
drive 6=$40.  That is nearly always the case unless there is a 2nd 
controller on the cable (yes that can be done!) then the 2nd controller 
would be setup to be address 6=$40.

Cheers, Gene Heskett
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