Date   : Wed, 14 Feb 2007 22:31:57 +0000
From   : hideki.adam@... (adam colley)
Subject: BBC Master 128 problem

Hihi

On 14/02/07, Richard Gellman <splodge@...> wrote:
> I've looked at the circuit diagram, and you'll be pleased to know this
> is a *very* simple 1-wire hack..

One wire! Nice -.o

> First, move LK18 or LK19 (depending on which socket you stuck the GoMMC
> in) back to its "Sideways RAM enable" position (east).
>
> This will leave a pin exposed. That pin goes solely to the _OE (output
> enable) line of the chip socket. You need to connect that pin to pin a2
> of your chosen cartridge socket (side "a" is the side nearest the back
> of the machine, pins are numbered left to right starting from 1, and do
> not alternate between sides, e.g. a2 and b2 face each other).

I did download the referencemanual but I'm assuming the diagram is
MASADV.A which I have no idea how to open -.-

> The entire sideways ram select is based on connecting the memory
> controller's bank select to either the relevant OE line on the socket,
> or to the DRAM CAS lines on the sideways banks (in accordance with the
> 4Mhz clock). The OE line is tied to +5V by a 4k7 resistor, and the pin
> left exposed on the link is a tap into this OE line. By connecting it to
> pin a2 on the cartridge slot you re-assign the OE line on that socket to
> be enabled by the cartridge OE line which works in an identical manner,
> but for sockets 0-1/2-3 rather than 4-5/6-7.
>
> -- end of technical bit --
>
> NOTE: Plugging a ROM cartridge into the hijacked cartridge slot would be
> *very bad*. At best it will confuse the system and make it hang/crash.

Ahh, I wasn't planning to do that, actually I have no cartridges of
any description so I might blow a couple of ROMs into a 25256 and
stick that in the other socket, I'd rather have everything inside the
machine o.0

Thanks ^^

-- 
Hideki.Adam