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What is this repository for?

This is a project for developing an adapter circuit board for Wave Share's Core3S500E module (an FPGA core board that features an XC3S500E device from the Xilinx Spartan-3 Family) that can be used in the TI-99/4A console.
Depending on your needs it can, like an Swiss Army Knife, be used in different manner:

  • It can completely replace Texas Instruments TMS9900 processor for creating a new FPGA based CPU by implementing a soft core.
  • It can provide additional hardware for use in parallel with the TMS9900 for example:
    • Co-processing, like math, graphics, DMA or a specialized GPL processor is possible.
    • Hardware debugging, like signal capturing or making internal CPU status visible, so you can check timing issues.
    • Realtime software debugging.
      • detecting invalid opcodes as a break option, so CPU get in HOLD condition and the debugger shows the point where the exception is happened.
      • setting break points via an interface (USB?) over PC communication.
    • Realize new hardware extensions, like:
      • memory expansions for CPU or GPL with mapping capabilities
      • new interfaces for USB, RS232 or flash memory
      • video graphic unit
      • and much more...

But all of these will only be realized within the FPGA, no extra hardware components will be needed. So, for those kind of hardware designs, there is an independent project called softcore99 witch resides in its own repository. But this repository contains everything to build the hardware basis, the infrastructure to provide the most flexible platform to realize all imaginable hardware designs.

Block Diagram

Block diagram showing how all components stuck together.