Gigatron Clone Ideas

[alastair]

Initial chip placement. The connectors and associated components haven't been added yet; they would go along the bottom edge. The gap is for the Pluggy Reloaded components. I left the option to use the existing Pierce Oscillator/6.25MHz crystal or you can use the can oscillator and divider (bottom left chip). The bottom right chip is for hi-res mode. I made room to install a 40-pin ZIF socket for the ROM. No video repeater though... I am thinking about adding headers to make it easy to install daughter cards for additional features/options. The board is designed to fit in a ZN-40 case. There's a power switch, but I still need to figure out where to put the blinken lights.

novatron.jpg (260.91 KiB) Viewed 166 times

[alastair]

Mostly routed. I was going to test the new design on a breadboard, but the only real change are the PALs. These can be reprogrammed so most of the debugging will be in firmware... assuming I didn't screw up the schematic. The ATtiny85 is on the board for the basic Pluggy, so it can be built to match the v2 Gigatron. I still plan to add the Pro Micro/SD Card on board for the Pluggy Reloaded option. 6-bit audio is standard with a single bi-color LED for a blinken light. Other options on board include the oscillator/divider for overclocking and 8 color hi-res mode with selector switch.

novatron.jpg (263.5 KiB) Viewed 114 times

[bjchapm]

This looks great. Very cool development.

[bmwtcu]

...the only real change are the PALs. These can be reprogrammed...

Very cool! I've only used GALs (which are reprogrammable) before, but I thought that PALs were OTP?

[alastair]

I've only used GALs (which are reprogrammable) before, but I thought that PALs were OTP?

I usually use GALs, specifically the ATF16V8B for development. I try and stick within the original PAL specs so you could build it with the vintage parts. I do have some NOS PALs for another project, but I still need to recompile the JEDEC file so I can program them.

[klf]

PAL16V8 is metal fuse PROM. GAL16V8 is EEPROM, HAL16V8 is mask ROM. 16V8 architecture is always the same.