@username@ wrote: ↑

Tue Mar 28, 2023 11:30 am

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?

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.

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 t...

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 b...

2 eprom games take up the whole 32k space while single eprom games occupy the lower 16 space (as far as what the hardware 'sees') The key with commercial (VTech) CV games is not how many EPROMs, but their size and how they are soldered in the PCB. That determines where each EPROM is mapped. 6K game...

Thanks pal. I should publish the fixed basic on the cvemu website as a download rom

Excellent thanks Tom!
Does this confirm that there's no mirroring made via hardware by the console?
All 32k ram area accessible normally?
L

Thanks @username@ excellent stuff!!

I look forward to someone having real hardware being able to test and post results

To overcome the lack of RAM - both HAPMON and the Shop advert thing had an EEPROM at $4000. The EEPROM at $4000 serves as "bank /ROM1" and is read as normal data. The use of a writable EEPROM (as opposed to an EPROM or PROM) is so that you can store the text permanently, even when the console is sw...

With the MegaSDCart you have all 32K to poke to - so knock yourself out :0) That's because the CV maps the 32K perfectly on the cartridge, using the /ROM1 and /ROM2 pins each covering 16K. This is shown in Tom's diagrams of the CV cartridge slot for MK1 and MK2 (which are slightly different). But t...