Custom cartridge with AY38010 sound chip.
http://f.rdw.se/AY-3-8910-datasheet.pdf
https://www.mdawson.net/vic20chrome/cpu/mos_6500_mpu_preliminary_may_1976.pdf
https://hackaday.io/contest/18215-the-1kb-challenge
https://hackaday.io/project/18536-atari2600-sound-cartridge
http://datasheet.octopart.com/FM1808-70-PG-Ramtron-datasheet-8328945.pdf
The FRAM programmer is from my [https://github.com/topherCantrell/GameBoyColor-Development](GameBoy programming project).
The chip on the left is a Parallax PropStick USB. The chip on the right is the FRAM 1808 chip. A java program sends data to the propstick over the the USB serial port. The propstick bit-bangs the FRAM chip's pins to program the RAM. The SPIN code (propstick) and the java code are in the repository.
Here is how the programmer is wired.
Before I make a custom board, I'll breadboard everything. I pulled the ROM off an Asteroids cartridge board and soldered on break-out wires. From right to left: GND, D0-D7, A0-A12, 5V.
This is a close-up of a Combat cartridge board without the ROM. Notice the missing A11 pin. The Combat game is only 2K bytes.
AY38910 control signals:
Mapping the AY38910 and the FRAM into the memory space:
