Date   : Fri, 08 Sep 2006 18:19:32 +0100
From   : Andrew Benham <adsb@...>
Subject: Re: Master AIV SCSI

Ian Wolstenholme wrote:
> Here's a picture of the resistor pack in my Domesday SCSI Board:
> 
> http://www.beebmaster.co.uk/Downloads/SCSITerm.jpg

Actually, we've got 5V being applied to the power line of the
resistor pack.  It's a 16 pin DIL, so presumably has power,
ground, and 14 resistor pairs.
If all 14 lines are pulled low, we have 14 lots of 5V across
220 ohms - which I make 1.6 watts.
If all 14 lines are pulled high, we have 14 lots of 5V accross
330 ohms, which I make 1 watt.

It's going to run quite warm then.

> On a general point about this particular SCSI interface, has anybody 
> successfully connected up a SCSI device other than the LV-ROM player?
> 
> I would be interested in seeing how VFS accesses the SCSI interface, I
> think if an amended version of ADFS could be made to look at the 
> SCSI interface for devices instead of the 1MHz bus then it could open
> up all sorts of possibilities.

An interesting thought.  How is the LV-ROM player interfaced to the
BBC Micro ?  Is there an image of the VFS anywhere ?

It might well be that the VFS implements a more complete SCSI
protocol (i.e. uses the ATN line), and we might be able to interface
to more recent SCSI disks.

-- 
Andrew Benham         adsb@...       
Southgate, London N14, United Kingdom

The gates in my computer are AND OR and NOT, not "Bill"