Posted By
crock
on 2020-11-25
06:17:36
 |  Re: Video Tutorial DIY Eprom For Commodore Plus 4
I see your problem now. The BASIC 7 cartridge is designed to run from the C2 cartridge bank, and not C1. If you look at the schematics, the banking logic in the 264 series allows the selection of 4 different sets of ROM's, each of which is split into the Low (8000-BFFF) and High (C000-FFFF) section.
The first set of ROM's is the BASIC and KERNEL, the second is the FUNCTION ROM's in the Plus/4 only (not connected on a C16/116), and the third is where most normal cartridges sit, which includes all the Commodore ones I've seen. The signals that select these cartridges are known as C1 Low, and C1 High, which are mapped to pins 'B' and '6' respectively.
However, there is a little used ability to also have a fourth bank of ROM's on an external cartridge, which is where BASIC 7 expects to be, which is selected by the signals C2 Low and C2 High, pins '7' and '8' on the cartridge port.
Looking at the GitHub page of the OpenC16Cart, the creator has not implemented the signals for C2, so you cannot use this cartridge for BASIC 7 in its current form.
On the plus side, I looked at all the binary images you created and they are all fine, so you did nothing wrong, and the 2 BASIC7 images you included are identical. I also compared the image you burned to the one read back from the EPROM, and that is mostly similar apart from the 2nd and 4th copies of BASIC7 have a different and rather cryptic start up message "YOU CAN FREEZE LIKE A 30 CENTURY MAN" 
Also, you might want to download a Hex Editor tool which makes it much easier to manipulate and compare binary files. I use one called "HexEdit" , but sadly looks like that has been discontinued.
Rob
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