Single Board Steckschwein

The single board Steckschwein marks several major milestones in the development of our favourite homebrew computer. The goal has alwas been to integrate the various boards onto one single PCB.

Specifications

• 65c02-CPU @ 10MHz

• 512k RAM

• 32k ROM

• Video chip V9958

  • Video RAM: 128 KB + 64 KB of expanded VRAM (optional)
  • Text modes:
    • 80 x 24
    • 32 x 24
  • Graphics Resolutions:
    • 512 x 212 (4 or 16 colors out of 512)
    • 256 x 212 (16, 256, 12499 or 19268 colors)
  • Sprites: 32 (max 8 per horizontal line)
  • Scroll registers

• Sound chip YM3812 (OPL2)

  • 9 voices
  • 2 oscillators (operators) per voice
  • 4 waveforms (sine, half-sine, absolute sine, pseudo-sawtooth) per operator

• rs232 via UART 16550

• SPI used as main peripheral bus for:

  • sd-card based mass storage
  • PS/2-peripheral controller (keyboard, mouse) (ATmega8)
  • RTC (Maxim DS1306)

Memory Map

For a detailed description on how our banking scheme works, see this post and also the slides from our talk at CVFe 22.0.

512k RAM organized in pages 16k each

Slot 0 is special, since it also contains the zero page, the stack (as given by the 65C02’s design) and also the IO-area.

The IO-area consists of 16 byte areas for the peripheral devices to be mapped in and also 4 internal registers to control the memory mapping.

The four “banking registers” are used to select the memory page to be mapped into which slot. Writing 0 into the banking register for slot 0 ($0230) will map the first 16k of the 512k into slot 0.

Pinouts

Connectors on the Steckschwein are more or less standard like PS/2, RS232, s-video. RGB is “inspired” by the NeoGeo Console, who used a standard 8pin DIN-Type connector for RGB, Composite Video and Audio.
User Port and the espansion slots have custom pinouts, of course.

S-Video

RGB

Expansion Slots

User Port

JTAG

This connector is used to program the CPLD