Date   : Fri, 25 May 2012 12:05:06 +0100
From   : jim@... (Jim Hearne)
Subject: Setting jumpers SCSI IDs

I'll have to remember that early SCSI can be reversed, i didn't start 
playing with it until it was on some PC's
I agree, it's easier for TTL logic to work that way round as the inputs 
float high when unconnected.

Jim

-----Original Message----- 
From: Johan Heuseveldt
Sent: Friday, May 25, 2012 10:56 AM
To: bbc-micro@...
Subject: Re: [BBC-Micro] Setting jumpers SCSI IDs

Hi,

On Fri 25 May, Jim Hearne wrote:

> >putting a jumper on makes it a value of '1',
> >and getting it off makes it '0'
>
> >The jumper list started with all jumpers off, and says SCSI ID = 0
>
> This is certainly the standard for all PC and Mac SCSI devices I've ever
> come across.

It's new to me!

Older drives /do/ work the opposite way, which seems the simplest
for the HW in those days.
(discrete non-inverted buffer with VCC pulled up signal line)


The Tape drive mentioned, is indeed of this kind.

[snip]


Yes, I have to take into account that the other way is the normal
way nowadays!

Thanks.


Greetings,
Johan

-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place

Avoid commas, that are not necessary.



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