[v1.1] MECB 1MB ROM Expansion Card

[epaell]

That's great. The rom checksum might be my fault - it's something I should automate better in my process and I'll need to check regarding the missing rom - thanks for pointing that out. I did run into the something like your serial problem - though now I've forgotten how I resolved that (and I don't have a working system at the moment to check). Which operating system are you compiling under? I also realise that I've probably hijacked this thread topic and should really create a new one specifically for MAME-related things.

[epaell]

I've created a new thread in the software->other section of the forum.

BTW, where did you see reference to "biosev.rom"?

[djrm]

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[djrm]

Extra supplies of 16v8s arrived this week, i've used them to add creativision mimic versions of the PLDs, this has allowed me to run the sonic invaders rom from the 1M expansion board. so far, so good. The plan is to be able to run the basic rom but I have a couple of problems,
1) the rom is 12k but there seems to be some confusion about just where in memory it sits. On the other forum I saw a post saying it is actually two roms part at 7000-7fff and another at A000 to Bfff
2)when the monitor at 7800 to 7fff is included then the total is bigger than the 32k rom space in the default ROM expansion settings. Hopefully another re-jig of the PLD code will allow this to run ok, assuming the stated addresses are correct.

n.b. so far I have ordered 15 PLDs from AE, just one unusable so far.
I have four 28c256s, one has a few bad bytes, others ok.

Reading some more, is there really only 1k memory available or does the basic cartridge have some more ram inside?

[epaell]

I have no idea of the creativision details myself but the MAME implementation may give some clues. On the face of it, it does look like there is only 1 KB of memory:

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	map(0x0000, 0x03ff).mirror(0x0c00).ram();

And there are two banks of ROM that can be up to 8 KB each:

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	map(0x4000, 0x7fff).rom().share(BANK_ROM2);
	map(0x8000, 0xbfff).rom().share(BANK_ROM1);

Loading the BASIC ROM into MAME (and running in debug mode) and looking at the memory map while comparing to the ROM contents it seems that the upper 4 KB of the ROM is replicated to 4000-4FFF, 5000-5FFF, 6000-6FFF and 7000-7FFF. The lower 8 KB of the ROM is mapped to 8000-9FFF.

Not sure if that helps or just confuses matters more.

[djrm]

Ah well that's back to front compared to how I was trying it, I'll test again in the morning. Thanks for your help. I couldn't get creativision working in mame. Not sure where to put the roms, bios seems to have been found though, strange. David.

[epaell]

I think you can put the ROMs anywhere, when you start it up you need to press Fn-delete (at least on my Mac that's the key combination to enable the menu). Then hit the "Tab" key to bring up the menu, select File manager, then Cartridge, navigate to where you placed your rom and select it. It should then start up with the ROM.

[djrm]

Swapping the two parts as suggested by Emil has resulted in Basic-1983 booting. I shall now try and patch the bios to read keys from the UART. Cant wait to get Greg's Creativision keyboard but that will have to wait a bit.



It didn't work at first for a couple of reasons, firstly I messed up placing the sections in the rom. I found this by enabling the UART in a new PLD, then loading SMON instead of Creativision Bios to check the data was as expected, it wasn't!

At one point during the process I turned off the MECB and pulled the TMS9929 board and noticed the power led flash on briefly as I put it back again - Last time this happened it killed the TMS9929, something strange happened this time too but it seems to have recovered now. perhaps the flash got corrupted I don't know. The TV monitor has a floating ground which could be the cause of the problem but I thought I'd fixed that.

The purpose of all this exercise is to be able to write a colour bar test program using BASIC - it should just fit in 1K RAM with a bit of luck, perhaps the full 4k will be available on this system, or maybe I can emulate a memory expansion somehow.

I still haven't managed to get mame running with the Basic ROM, something for another day, perhaps have a look during the coming summer holiday, not long now.

Thanks again for the help, David.

[epaell]

Hi David,

It's great that the swap worked.

I'm curious what failed with MAME? Were you able to select the ROM to load? Are you running the crvision emulation? In case it helps you can also specify the path on the command line e.g.

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./mame -window -debug -resolution 640x480 crvision -cart /full/path/to/mame0246-x86/roms/crvision/BASIC82B.BIN

This also sets it up to run in a smaller window and enables debug mode (I had my basic cartridge in the same location as the other ROMS but it shouldn't matter where they are).

[djrm]

I've forgotten most of the little I learned about mame singe starting with the real MECB, I'm happier with the command line approach. I hadn't realised there was a -cart parameter to load the roms either, I can now play the basic rom using a variation of your sample command, nice.

Typing in mame is a chore with its funny key mapping but I found enough characters to type in the sample bars program from the manual, a result:


Now I need to get something like this working on the hardware ...