[Color Computer][Coco] Tandy Hard Disk Controller

[Mark Marlette]

Gene,

I would have to go pull the 500 page spec out again. You seem to be up on it.

Can you tell me how they are doing collision detection?

This is how SCSI works on the TC^3 Interface.......

SCSI devices communicate with each other by sending data packets 
across a shared bus. The device uses a hardware handshake to acquire 
the bus--all other devices must be silent while another device uses 
the bus. Unlike Ethernet, the bus is not accessed using a collision 
detection mechanism. Instead, devices follow a stateful algorithm to 
acquire the bus. When idle, the bus is in a state, or phase, known as 
the bus-free phase. If a device wishes to access the bus, it enters 
an arbitration phase, but only if the bus was previously in the 
bus-free phase. Clearly, there exists the classic problem in mutual 
exclusion where two devices check the state of the bus, both finding 
it in the bus-free phase, and go into arbitration. In this situation, 
the device with the highest SCSI ID always wins.

Maybe you are confused with collision detection and Ethernet??? Not 
the case in SCSI.

Did you ever get your TC^3 running on your system after Boisy and I 
set it all up for you in a standard configuration?

Mark
Cloud-9



At 3/4/2006 05:43 PM, you wrote:

>On Saturday 04 March 2006 18:32, Mark Marlette wrote:
> >Test more than one CoCo on a SCSI drive?
> >
> >That would be a disaster.
> >
>It could be if the driver doesn't have collision detection, which I'd
>bet the farm none of them do.  I mean, this IS the coco we're talking
>about here folks. :)
>
>But the scsi specs themselves do have collision detection as a very
>important function, for exactly that reason.  For the coco though, that
>would mean that the middle 16 wires in the cable would have to be used
>as the handshaking to control that is in the middle of the connector
>IIRC.
>
>Does your tc^3 interface support that somehow?
>
> >Mark
>
>--
>Cheers, Gene
>People having trouble with vz bouncing email to me should add the word
>'online' between the 'verizon', and the dot which bypasses vz's
>stupid bounce rules.  I do use spamassassin too. :-)
>Yahoo.com and AOL/TW attorneys please note, additions to the above
>message by Gene Heskett are:
>Copyright 2006 by Maurice Eugene Heskett, all rights reserved.
>
>--
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>Coco at maltedmedia.com
>http://five.pairlist.net/mailman/listinfo/coco
>
>
>
>
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