Date   : Mon, 07 Oct 2002 00:05:19 +0100
From   : Sprow <info@...>
Subject: Re: Copying Paged eproms on a carrier

In article <004101c26dc8$8cf74fa0$af4e893e@...>,
   Alastair Seggie <alastairseggie@...> wrote:
> Hi all
>
> About a year ago I bought an old Denford Starturn 8 CNC lathe this runs 
> off a BBC computer Via the 1MHz bus. It has an EPROM that has to be 
> inserted in to the BBC before it will work.

[snip]

> Now the problem I have is that the EPROM I am talking about is not mine.

The 20 pin device is a PAL (or GAL) which hovers on a few address lines and
outputs a couple of chip selects.
One scheme I considered was to have branch locations at known points in the
ROM which were just
 .page0
 RTS
 .page1
 RTS
 .page2
 RTS
 .page3
 RTS
then to swap pages you push the desired routine address (-1) on the stack
and JMP to page<whatever>.The PAL then swapped the ROM round the processor
finds an RTS and everyone's happy.

Not sure if this is exactly how our lathe does it,but you might try swapping
the ROM for an Interword carrier to see if it still works.

> I also need any information on the "Multiprom" EPROM Programmer 
> specifically will it copy large EPROM's so I could copy this one. Any Info 
> on the programmer would be appreciated.

If it's small,beige,plugs into the user port with 8 DIP switches labelled A
and B then it can handle anything from 2764 (8k) to 27512 (64k),
Sprow.

> Alastair