Could somebody take a look at this?


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I started some time ago on creating a VHDL implementation of the sound board used in a number of Gottlieb video games and pinball machines. At the moment I'm using the Mad Planets ROMs as I own one but the board is identical to that used in Qbert and others sans SC-01 speech chip. The sound board is a simple 6502 based system that accepts input through 6 I/O lines on a 6532 RIOT and plays sound by latching values off the data bus directly to an 8 bit DAC. There is a pretty good explanation of how it works on and in fact it seems he already implemented the whole thing in FPGA but the code is not available so that aspect is yet another useless tease like so many other FPGA projects out there.


Anyway I had shelved this project at one point since it was beyond my primitive VHDL abilities but got it out again recently armed with a better understanding. At this point I'm seeing signs of life which is exciting but something is still not right. It starts up and when I press the test button on B6 it jumps into another state which means the setup and polling of the RIOT input port that button is on must be working. For some reason I'm never getting an interrupt out of the RIOT when the strobe line PA7 goes high and I'm not sure why that is. I've hit another wall and maybe just need an extra set of eyes on this, or somebody a bit more proficient with the 6502 and iSim. Attached is the project directory which should be everything needed.

Gtb sound

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