[v1.1] MECB 1MB ROM Expansion Card

[Editor]

Topic now updated (i.e. the first post above), with link to the Part 1 blog entry and video.

The ROM Expansion Card is now v1.1

It's been a busy start to the year for me, so this is my first new MECB hardware related post for 2024.

[bugeyedcreepy]

Topic now updated (i.e. the first post above), with link to the Part 1 blog entry and video.

The ROM Expansion Card is now v1.1

It's been a busy start to the year for me, so this is my first new MECB hardware related post for 2024.

Nice! Good to see you back into it - did I mention how patient I am?

Anyhoo, yet another suggestion - would it make sense to drop subsections into the various CPU forums for the systems we might configure these MECB systems into? i.e. a ColecoVision post under the Z80 forum, an Atari 2600 post under the 6502 (or 6507 if one were pedantic), etc? I imagine that'd be a sensible shortcut to config hints and tips, as well as plc specific configs and Q&A for the best hardware emulations, so on.

Also, thinking I might review & vlog my own builds of your kits - see just how long it takes me to run over myself...(?)

[Editor]

Nice! Good to see you back into it - did I mention how patient I am?

It's been a hectic start to the year. Mainly lots of "flood recovery" projects around the home, now the insurance has come through.

Anyhoo, yet another suggestion - would it make sense to drop subsections into the various CPU forums for the systems we might configure these MECB systems into? i.e. a ColecoVision post under the Z80 forum, an Atari 2600 post under the 6502 (or 6507 if one were pedantic), etc? I imagine that'd be a sensible shortcut to config hints and tips, as well as plc specific configs and Q&A for the best hardware emulations, so on.

Sounds like a good idea. Since the discussion about these systems would be mostly software related, I suppose just adding topics under the relevant CPU in the Software section would make sense. Go for it.
I expect the first system I am going to play with will be the CreatiVision (for personal nostalgia reasons). This was 6502 based.

Also, thinking I might review & vlog my own builds of your kits - see just how long it takes me to run over myself...(?)

Awesome. I look forward to it! Let me know your YouTube channel name, so I can subscribe!

[Editor]

I've just updated the initial post in this topic, to add the link to Part 2, which covers the initial testing of my 1MB ROM Expansion Card, which also involves resolving a logic error, before finally completing the testing of my first assembled card.

[bugeyedcreepy]

I've just updated the initial post in this topic, to add the link to Part 2, which covers the initial testing of my 1MB ROM Expansion Card, which also involves resolving a logic error, before finally completing the testing of my first assembled card.

Ooh, Bring it On, Big Buddy! And I've already raided my piggy bank, so Lay It On Me!!

[Editor]

Ooh, Bring it On, Big Buddy! And I've already raided my piggy bank, so Lay It On Me!!

Thanks! I've just finished packing your order, ready for the next courier pick-up (in the morning). It's been a busy day today, so order fullfilment was a bit later in the day than usual. But, I always make sure that any orders are ready for the next courier pick-up!

Then, tomorrow, I must get started on my next video.

[bugeyedcreepy]

Thanks! I've just finished packing your order, ready for the next courier pick-up (in the morning). It's been a busy day today, so order fullfilment was a bit later in the day than usual. But, I always make sure that any orders are ready for the next courier pick-up!

lol! I'm forever getting stuff from China that takes months in some cases, I'm pretty sure I'll survive a short delay, despite my excitement!

Then, tomorrow, I must get started on my next video.

Go, you good thing, GO!!

[epaell]

Is it possible to program the ROMs using the processor? I noted the board has a "write enable" jumper and I thought I saw this mentioned somewhere on the forum but I can't seem to find it again. However, after a quick look through the data sheet for the device it looks to me like access to the full address bus (or at least the first 15 bits) is needed to send the appropriate commands for writing to it. With only 16KB (14 address bits) available at a time I guess that's not possible with the current set up?

[Editor]

Is it possible to program the ROMs using the processor? I noted the board has a "write enable" jumper and I thought I saw this mentioned somewhere on the forum but I can't seem to find it again. However, after a quick look through the data sheet for the device it looks to me like access to the full address bus (or at least the first 15 bits) is needed to send the appropriate commands for writing to it. With only 16KB (14 address bits) available at a time I guess that's not possible with the current set up?

Yes, although I haven’t yet tested this, my reading of the datasheet indicated that writing of the FLASH ROM should be achievable (in 4KB blocks), as long as you are using at least a 32KB bank (i.e. ability to present the A0 - A14 address lines).

This is required for presenting the software data protection address code sequence.
Once the software data protection sequence is completed, an erasure of a specified 4KB block (within the currently selected bank) would first be completed, followed by the byte-by-byte sequence written (programmed) within the erased 4KB block area.

So, yes, you are correct that this wouldn’t be achievable with the 16KB bank setup that I’ve initially setup my PLD for. I chose this bank size as a default setup, thinking that most users would want the larger 48KB RAM space.
However, the Card can be configured for whatever ROM space(s) you want to allocate within the 64K addressing space of our existing CPU Cards (or even the full linear address space with future 20-bit addressing CPU Cards).
However, you do of course need to re-program your “glue logic” PLD to achieve this.

Note also, that the code performing the ROM write operations would need to be running from RAM, as the ROM content is not available for a read operation until the completion of the erasure / programming operation.
If to be a function of ROM based code, this would first need to be programmatically relocated to RAM for execution outside the ROM.

The ROM Write jumper was included on the ROM expansion card (like on the CPU Card), to allow exploring / experimentation with this possibility.
The thinking being that this might be useful for storing things like non-volatile settings, and such like.

[epaell]

Great, thanks for confirming this. I was just pulling the FLASH chip and out quite a few times to get BASIC running on the 6502 and was thinking this can't be great for the chip or socket ... and then thought it would be nice to be able to program it in situ (via some simple bit of code to send the appropriate commands to the FLASH ROM).

I guess the simplest solution would've been if I installed ZIF sockets rather than standard sockets Or, as you say, perhaps use a prepared PLD with the 32 KB ROM space that I can use for these occasions (though that'll just shift the stress from the FLASH ROM to the PLD/PLD-socket) - I might try this at some stage just to "play" with the write option at some stage anyway (to satisfy my curiosity).

Another, more involved option might be to set up a MAME equivalent of the MECB and make sure the code I'm burning works there before doing the actual burn. Perhaps something also worth playing with - though I'd have to admit that I somehow never find simulated systems quite as satisfying as the real thing