[OT] SCSI Printer on AIC78XX without SCSI Terminator

[OT] SCSI Printer on AIC78XX without SCSI Terminator

[Gustavo Guillermo Pérez]

Hello, I was tried to use a SCSI Printer, onto a AIC78XX (old and new driver), 
when driver load, it recognise the Scanner, the Printer and Panel, but may be 
the copier doesn't have an internal terminator, and driver hangs forever 
discovering unexistent 4th device. I do not wish to dissasemble the copier to 
solder the terminator, and I never deal with SCSI HW. Kernel I was tried: 
2.6.7, 2.4.23. but I think the driver does not change from 2.6.7 to 2.6.12.

I see the doc about this driver but I can't figure out wich of a lot options 
can help to not try to discover more than 3 devices... I'll have a chance to 
play with this machine the next week, then I'm taking ideas.

aic7xxx=seltime:2
this option wait for answer but the device 4º waits forever...
aic7xxx=no_reset
I don't....
aic7xxx=override_term
mmmmmm
....

The new driver support cmdline args?

If someone can share comment I would appreciate it

cheers
-- 
Gustavo Guillermo Pérez
Compunauta uLinux
www.compunauta.com

Re: [OT] SCSI Printer on AIC78XX without SCSI Terminator

[Brian O'Mahoney]

First, normal (non-differential) SCSI is an OpenCollector bus design
which simply wont work without a terminator and is designed to use
exactly two(2) terminators, one at each end of the bus, these both
provide a pull up and terminate the bus to prevent reflections. Also
the longer and faster the bus the more you depend on correct termination
e.g. 130 ohm - +3.3V

For much more detail, including external terminators please see

http://www.scsita.org/aboutscsi/SCSI_Termination_Tutorial.html

Second, there is usually a built in terminator in the AIC7xxx
adaptor, usually enabled in the SCSI BIOS.

Also check your device for negotiable SCSI options, eg SYNC, OFFSET

Gustavo Guillermo Pérez wrote:
> Hello, I was tried to use a SCSI Printer, onto a AIC78XX (old and new driver), 
> when driver load, it recognise the Scanner, the Printer and Panel, but may be 
> the copier doesn't have an internal terminator, and driver hangs forever 
> discovering unexistent 4th device. I do not wish to dissasemble the copier to 
> solder the terminator, and I never deal with SCSI HW. Kernel I was tried: 
> 2.6.7, 2.4.23. but I think the driver does not change from 2.6.7 to 2.6.12.
> 
> I see the doc about this driver but I can't figure out wich of a lot options 
> can help to not try to discover more than 3 devices... I'll have a chance to 
> play with this machine the next week, then I'm taking ideas.
> 
> aic7xxx=seltime:2
> this option wait for answer but the device 4º waits forever...
> aic7xxx=no_reset
> I don't....
> aic7xxx=override_term
> mmmmmm
> ...
> 
> The new driver support cmdline args?
> 
> If someone can share comment I would appreciate it
> 
> cheers

-- 
mit freundlichen Grüßen, Brian.