Schneiderware Pseudo ROM

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The Schneiderware Pseudo ROM is a expansion "ROM" board, with 16K EPROM (read-only) and 16K battery-backed SRAM (read/write-able), published by german magazine CPC Schneider International as part of their Schneiderware DIY series. The plain PCB, or the fully assembled board were also available via mail-order.

The ECB Bus connector of the board is intended to be plugged into the Schneiderware Basisplatine, but it could be also wired directly to the CPCs Expansion Port.

Databoxes: UHR8000 RTC-RAM-driver in 10-1986 (hex listing, plus Hisoft Devpac source code) (caution this version uses incorrect I/O addresses FBE1-FBE3), UHRC000X RTC-ROM-driver in 4-1987 (this version uses correct I/O addresses FBE2-FBE4). Uni-PIO examples in 12-1986 (=only a few basic lines). There seem to be no Centronics and V/24 drivers included in databoxes.


  • Schneiderware #8 Pseudo ROM (SRAM and EPROM mapped as ROM) (4/1987 pages 26-34, plus corrections in 5/1987 pages 32-34)

I/O Ports

Address (default) Address (alternate) Usage
DFxxh N/A Schneiderware RAM/EPROM - Expansion ROM bank number (W)
Battery-backed SRAM and/or EPROM are selected when the bank-number matches the jumper-selected values; the memory is then mapped to C000h..FFFFh (in case of READing one must also enable upper ROM via Gate Array). The bank number decoding is a bit strange:
  • EPROM/Read bank: All 8 bits decoded (bank 00h..FFh)
  • SRAM/Read bank: Only lower 4 bits decoded (bank X0h..XFh)
  • SRAM/Write bank: Only lower 4 bits decoded (bank X0h..XFh)

The SRAM/Write mode doesn't disable the internal RAM in the CPC, so writes are going both to SRAM and normal RAM at C000-FFFF, that no matter if upper ROM is enabled/disabled via Gate Array; the author recommended to map VRAM to 4000-7FFF via CRTC registers, in order to prevent video dirt during writing.