ZXpand ROM overlay

[nollkolltroll]

I'd be very happy if someone (Moggy?) could show me how to load a different ROM-image from ZXpand instead of the original one.
It should be possible, except for the character definitions. Unfortunately my searches and reading the manual has yielded no result.

[Moggy]

I'd be very happy if someone (Moggy?) could show me how to load a different ROM-image from ZXpand instead of the original one.
It should be possible, except for the character definitions. Unfortunately my searches and reading the manual has yielded no result.

Hi Adam.
As the Xpand ROM works together along side the original ROM I don't know of any way to replace it as I don't have the brain for it.
Charlie, Andy, Mark or Pokemon etc are the forum gurus for the hardware.

What I have been able to do , however is to take advantage of what I believe to be one of the more powerful aspects of Charlie's wonderful creation, IE its ability to store data/program code at an address of one's choosing.

In simple terms I take the code stored in the EPROMS of certain devices mainly Memotech say memocalc, Z80 assembler that kind of thing and poke the code to a large REM.

I then turn the REM into a P file and with a simple basic loader I then load the code into the Xpand at the memory address space the original Memotech EPROM would have occupied.
In the case of the Z80 assembler for example the P file is loaded I think at 12288 onwards then by way of a simple USR call as per the instruction manual the Xpand behaves like the original Memotech module.

This won't work for all the Memotech modules like say the HRG one as it has a press button to switch between the two display modes which is not there on the Xpand.

This thread here....

viewtopic.php?f=8&t=1532&hilit=z80+assembler

Has the download for Memotech Z80 assembler EPROM the basic loader the P file and the Memotech manual, the loader sets memory to either high or low, I forget which, so no need to worry then resets the zeddy , ramtop should be set as per the instruction manual example supplied.

While this does not replace the Xpand ROM in the manner I think you desire it is a fun thing to play with and saves wear and tear on original units.
Hope this helps a little

[sirmorris]

That's right, there are a couple of ROMs which would originally live in the 8K region. ZXpand doesn't offer RAM at 0 to 8K so it's not possible to load alternative ROMs there. Sorry!

[nollkolltroll]

Ah, that's why I was confused! I knew about the loading of ROM-images, but missed that they were originally in the 8-16k region.
Oh well, back to trouble-shooting my eprom-emulator.
Thanks for your quick replies!

[1024MAK]

It is possible to build a custom RAM expansion. The RAM will be read and write enabled in the high RAM area (32k to 40k) area. So you can copy your code to it. Then you can select to page out the ZX BASIC ROM and page in RAM in the 0 to 8k area for read only access (saves the problem of ROMs writing to themselves).

Wilf's web page gives details Thanks for the Memories

Mark