Cartridge ROM mapping

[MADrigal]

Thanks Tom. I didn't dare mentioning the Meg SD cart cause I wasn't too sure if it used a modified bios at $f800 (bypassing the existing bios entirely) or in the usual 32k rom space.
Also cv mark 1 and 2 have different address lines so it's important to know if and how you can use the upper 16k on both.

[Scouter3d]

Also cv mark 1 and 2 have different address lines so it's important to know if and how you can use the upper 16k on both.

The upper 16k can be used on mark 1 and mark 2 without problems... (CSL and MegaSDCart work in both revisions)

but i think there always needs to be the 2k BIOS (either the original or a modified one, but then again even that could be replaced by something totally different (if someone wants to create a new BIOS :0) ))

Cheers, TOM:0)

[MADrigal]

I believe as long as there's something the 6502 accesses and executes at startup, anything would do. Bios, or a game or a program doesn't matter. What is important is to know whether the console has logic suitable/sufficient to disable the original bios so it can be bypassed. thanks for confirming this!!

[Scouter3d]

Here is a short "summup" of the cartridge-port address-signals, that can be used on both revisions...

The MK II port has replaced a few signals, that where present on MK I with signals needed to allow for an external CPU...

The MK II cartridgeport misses:
PIN 17: A15 (replaced by /CSW)
PIN 18: A14 (replaced by /CSR)
PIN 36: +12V (replaced by "switch to external CPU" signal)

Instead of the missing A14 and A15 the "16k block-select signals" can and should be used to address:
PIN 29: /ROM1 ($8000 - $BFFF)
PIN 32: /ROM2 ($4000 - $7FFF)
PIN 33: /ROM0 ($C000 - $FFFF incl. the 2k BIOS)

/ROM0 is on both revisions wired so, that it first goes to the cartridge port and "normally" an inserted cartridge would shorten the /ROM0 on PIN 33 to /ROMR on PIN 34 to "enable" the BIOS selection. That´s also why a Creativision without cartridge does "nothing" when powered on...

But /ROM0 could also be used to select an external BIOS/Program on the cartridge and not connect it back to /ROMR to use an external BIOS (like in the CSL Cart or MegaSDCart). Also only "parts" of the original /ROM0 select can be given back to /ROMR. That makes it possible for the parallel I/O Modul to use part of the /ROM0 addressroom and still use the original internal BIOS.

here is the pinout again to round this up :0)

Cheers, TOM:0)

creativision_cart_pinout_v3.jpg

[MADrigal]

Excellent Tom this clarifies everything
It would be good to wrap all the info in a single document or article to share from the website, to give it more visibility.

[MADrigal]

I took the executive decision to fix the byte at $7223 for BASIC - saves writing and having a panic attack

Can you please share the patched BASIC rom here?

[@username@]

The ROM is not patched as such, only when it's injected into the image.

[@username@]

Attached is BASIC83B with the entire CVDEMO tape included, in both flat and AB images.

Use CLOAD or CRUN to load from the now free ROM space.

Enjoy!

[Scouter3d]

Attached is BASIC83B with the entire CVDEMO tape included, in both flat and AB images.

Use CLOAD or CRUN to load from the now free ROM space.

Enjoy!

Hi @username@,

i gave the cartimage a go on real hardware and it works like a charme! :0)

PS: I tried the "flat" version.

Can you please provide a small "how to" get a BASIC Program in the right format / cartridgespace for this awesome design?

Cheers, TOM:0)

[@username@]

Can you please provide a small "how to" get a BASIC Program in the right format / cartridgespace for this awesome design?

There is no actual design - more a kind of organic cobbling together

I've attached the DIY manual and tools - but I will probably update the utility part over time, as I'm sure there will be a wee buggette waiting for me!