Date   : Thu, 02 Jun 2005 06:34:17 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: Zif thingy

In article <F2CBAA61037E48B8A9A7877D72D56022.MAI@...>,
BeebMaster <beebmaster@...> writes

>The ROM Box I have was made by Micro Pulse.  There are some pictures of
it here:
>
>http://www.beebmaster.co.uk/GreatestFind/ROMBox.html

I have the MicroPulse ROMBox board - a local electronic shop was selling
them off as scrap for a few pennies each many years ago and didn't know
what they were.  Once I found the solder short, it worked fine and still
does to this day.  Boxed it up in my own housing, which I have to say is
much more attractive than the MicroPulse one.

It's actually plugged into an adapted "Care" ROM cartridge, which then
goes into the ashtray socket, so the cable is about a metre long in
total.  Never had a problem with it.

>I haven't taken it to pieces but I should think it's a fairly simple design 
>which could probably be
>replicated for a home project.

It is very simple.  Just a couple of buffers and some simple logic for
the rotary selector switch, the ROM sockets, and LEDs, resistors and
decoupling caps.

>  I would warn you about the problems I have had 
>with it though.  It
>really did cause havoc with the Master it was attached to; squiggles on start-
>up, unusual errors,
>sudden crashes etc etc so I would only do it if absolutely necessary.

Well, it was designed to work with the BBC B, though I can't see why it
wouldn't work with a Master.  If the TTL buffers (74LS244/245) are
socketed, it might be worth trying faster ones (74HCTxxx or 74ALSxxx).

Mike