3 Sep
2006
3 Sep
'06
11:48 p.m.
jim stephens wrote:
Yes, I can recall the cross-sectional illustration of the
cable (I have the SCSI-2 spec here along with ENDL's bench
reference...). No, Jim, I wouldn't be inclined to use an
RS232 cable to connect the two DB25's! :>
But, the only way I can *guess* that a cable is "suitably
designed" is to *infer* that since it has, e.g., DB25 on one
end and Centronics50 on the other, it *seems* likely that
this was it's intended purpose (though who knows how much crap
was spilled onto the Mac market, etc.)
Don wrote:
> But, it's got those wacky DB25 SCSI connectors. :-/
>
> I have DB25-Centronics cables. And, DB25-HD50 adapters.
> The scanners have a hodge-podge of *different* connectors
> (sheesh! talk about "standards"... :< ).
E.g., how much
grief can I expect going *through* the slide
scanner with DB25 coming in and Centronics going out? Is
this just effectively a "DB25-Centronics" adapter with a
device tap in the middle?
The main thing to worry about when the DB25 is involved
is that the cable that is used is scsi certified. The round cable
that is usually used between the two connectors if it is there
has a special way of positioning the req and ack signals in the bundle of wires. Other than that, the standard
specified
the connector, so that should be no worry.
I know early on, some cables were made and just used that
may not have been SCSI certified, and in early "vintage" systems
you may run across such, and have noise or performance
problems with the devices, if the REQ / ACK / Select signals
get messed up.
Only when you go from 50 -> 68 pin should you beware of
termination on the upper 8 bits added by the extra lines and
what you have for an initiator and targets.
Yeah, no problem there.
There is not much science in a wide initiator
selecting narrow
devices on a chain, but there is when you have wide targets and
a narrow initiator.
but you don't have that from what I read, so it is just a matter
of haveing a bit of everything in the chain connetorwise, but
the SCSI bus should all be the same.
Thanks! I guess I'll just do the "cross fingers and hope" trick.
At least any problems will be more "visible" (and, less *hazardous*
than if the devices were disks, etc.).