Tandy Speech/Sound Cartridge

The S/SC is a device that you attach to the Tandy Color Computer’s cartridge port. It contains a microcontroller that allows access to a SP0256-AL2 speech systhsizer and a AY-3-8913 programable sound generator.

Component

More information

Speech/Sound Cartridge Service Manual, User/Programmers Guide
SP0256-AL2 (Speech Processor) Datasheet, Web Sites
AY-3-8913 (Programable Sound Generator) Datasheet, Web Sites
ROM (inside the PIC7040) Binary, Commented Disassembly (2/20/2022: unfinished)
Disk image of S/SC Programs Direct Link
Pictures
Box sscbox.jpg
Manual sscmanual.jpg
Cartridge sscpak.jpg
Technical Dissucssion of how the Microcontroller Operates the Device

A good resource to have is the TMS7000 data manual. The manual can be downloaded here. During this discussion it would be handy to have the schematic (found in the service manual) for reference.

The TMS7000 used in the S/SC has four data ports:

  • Port A – Input only. Used to recieve information from the CoCo.
  • Port B – Output only. Used as the lower 8 bits of the address bus to the 2k of RAM.
  • Port C – Bidirectional. Multifunctional, see below.
  • Port D – Bidirectional. Forms an 8 bit data bus used to communicate with the other compenents.

The TMS70x0 has three interrupts:

  • INT1 (highest priority) – Signal from the speech chip that it finished speeking, and is ready for a new allophone.
  • INT2 (middle priority) – Internal timer interrupt.
  • INT3 (Lowest priority) – New data from CoCo.

The TMS7040 has three Registers:

  • PC – Program Counter (16 bits)
  • SP – Stack Pointer (8 bits) Stack can only exists in first 256 bytes of memory map.
  • ST – Status Register (8 bits)
    • Bit 7: Carry Bit
    • Bit 6: Negative Bit
    • Bit 5: Zero Bit
    • Bit 4: Global Interrupt Enable/Disable bit
    • Other bits unused