Denial

Does anyone have any utilities that allow testing of the read signal from a datasette? I had some utility programs for my C64 for azimuth adjustment, something like that would help if it ever existed for the VIC. I'm trying to get a cassette interface to my FPGA based VIC20 working, but it won't rea...

If CA2 is driven as a result of an external RC network, then the test results would not be deterministic because the results would be dependent on the component tolerances of the external analog circuit, hence why I was suggesting masking that bit. Anyway, from some math it seems possible that the c...

Interesting, so at least that kind of confirms that the test results are good, the VIA in my VIC is bad, and yes I am aware that VICE has the VIA shift register badly wrong. So its looking like the cassette motor drive is interacting with the CA2 pin when its configured as an input. Looking at the s...

I am hoping someone can clarify the state of the CA2 on VIA#1 ($9110) on a real VIC. I'm working on validating the operation of the VIA's in my own FPGA based VIC20 and for this I am using the tests from VICE, however some of the tests for the shift registers give a state of the VIA Interrupt Flag R...

I spent a good few days going through the assembler of the diag cartridge ROM, the issue I had was in the ISR. On entry the ISR reads $9C00 and does a logical AND with $01 and loops based on the result. LAA07: ; << ISR >> LDA X9C00 AND #X01 BNE XAA07 On my FPGA VIC20 implementation that caused an in...

Hi, I've already posted this over on the Lemon forum and they suggested posting here ! I've built an FPGA based version of a complete VIC20 with 3K RAM expansion and to test this out I thought it might be a good idea to use the Commodore diagnostics cartridge. The trouble is my FPGA VIC seems to han...