Schneider RS232 Interface

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RS232 Interface for the CPC by Schneider. Schneider is the german distributor for Amstrad CPC hardware (however, this interface seems to be Schneider's own invention, not an Amstrad product).

Note: The uncommon shape of the housing dates back to a Schneider BTX modul (which was being intended to be plugged into Schneider Television Sets). Apparently Schneider produced too many housings, and re-used them for the RS232 interface. Actually, a RS232 interface is very much the same as a BTX interface (the actual BTX modem must be rented separately from Deutsche Bundespost), so even the PCB may be (almost/exactly?) the same for both devices.


I/O Ports

 F8E0h Z80 STI Indirect Data Register       Read Write
 F8E1h Z80 STI Gen. Purpose I/O Interrupt   Read Write
 F8E8h Z80 STI Pointer Vector Register      Read Write
 F8ECh Z80 STI USART Control Register       Read Write
 F8EDh Z80 STI Receiver Status Register     Read Write
 F8EEh Z80 STI Transmitter Status Register  Read Write
 F8EFh Z80 STI USART Data Register          Read Write


Supported by "Starwriter".

Similar (or identical?) Interface

The circuit is very similar (or possibly indentical) to the Tim Riemann's RS232 interface, both circuits are using a Z80 STI, both mapped to the same I/O port addresses. Whether or not the circuits are fully compatible with each other is unknown. Some small details might differ. For example, the clock source being passed to the Z80 STI chip could be different.

Manual (german)

Datasheet (Missing)

  • A "Z80 STI" is a 40pin MK3801 chip from Mostek. Details on that chip are from the "MOSTEK 1982/1983 Microelectronic Data Book" (kindly made available by John Robertson).
  • The MK68901 seems to be a newer/similar chip (but neither port addresses nor pinouts are backwards compatible).