[Coco] Need help (of course)

[Gene Heskett]

On Saturday 06 December 2014 00:25:38 Arthur Flexser did opine
And Gene did reply:
> Al, my recollection is that the terminating resistor should go on the
> LAST drive on the cable, not the first.  No?  (The name "terminating"
> certainly would seem to suggest that.)
> 
> Art

That was the plan Art, not always critical on a slower floppy circuit, but 
absolutely a requirement for a scsi buss.

It can record and die on errors that are only a 10 ns duration.  A scsi 
circuit is also one of the best psu checkers I've found as its noise 
margin goes straight to hell in a resistive terminated setup when the PSU 
has only sagged .1 volts to 4.90 volts on the 5 volt buss due to aging 
components. "active" terminations don't suffer the noise margin loss near 
as quickly because their terminating voltage is regulated.

I can explain that further, but its in the archives already.
 
> On Fri, Dec 5, 2014 at 11:12 PM, Al Hartman <alhartman6 at optonline.net>
> 
> wrote:
> > What is normally done on TRS-80 Disk drives is that you jumper DS0
> > and DS1 on every drive. Put the terminator in the Drive 0:, and
> > remove it on all other drives.
> > 
> > Then, you remove the pins from the edge connector on the drive cable
> > for the unused drive selects, causing each connector to select only
> > one position with drive 0: being the furthest from the controller.
> > You can have 4 single sided drives this way. If you want to use
> > double sided drives on a Coco, I think you have to jumper ds3 to the
> > side select pin with a wire in both drives, and you can only have
> > two drives in DEB. OS-9 might let you have 3 double-sided drives,
> > but someone else would have to tell you.
> > 
> > -[ Al ]-
> > 
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco


Cheers, Gene Heskett
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