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Last modified on 30 September 2010, at 16:00

Schneiderware V/24 Interface

Revision as of 16:00, 30 September 2010 by Nocash (Talk | contribs) (→‎I/O Ports)

The Schneiderware V/24 Interface is a RS232 Interface, 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. The V/24 board additionally requires a Schneiderware Power Supply (or another external power supply with +12V/-12V).

  • Schneiderware #3 V/24 (RS232 Interface) (8/1986 pages 70-77, plus correction from 9/1986 page 80)

I/O Ports

Default I/O Addresses are F9E0h-F8E1h and F9ECh-F9EFh (ie. the lowest and highest addresses in the F9E0h-F9EFh region). Alternately, addresses F9E2h-F8E3h and F9E8h-F9EBh (ie. the middle addresses in the F9E0h-F9EFh region) are jumper select-able (intended to allow to connect two RS232 cards to the computer).

Address (default) Address (alternate) Usage
F9E0h F9E2h Schneiderware V/24 8251 USART chip Data
F9E1h F9E3h Schneiderware V/24 8251 USART chip Control
F9ECh F9E8h Schneiderware V/24 8253 chip Timer 0 (TX clock)
F9EDh F9E9h Schneiderware V/24 8253 chip Timer 1 (RX clock)
F9EEh F9EAh Schneiderware V/24 8253 chip Timer 2 (unused)
F9EFh F9EBh Schneiderware V/24 8253 chip Timer Control

Caution - The clock source can be jumpered to 2MHz (default), or to 1MHz. Moreover, the handshaking signals (CTS/RTS, DTR/DSR) can be disabled via jumpers. There is no good reason for using the 1MHz setting, nor for disabling handshaking at hardware level - these features are only "good" for provoking compatibility problems with software that expects the jumpers to be set to this or that position.

For the more bizarre part, the handshaking signals are disabled by default. And, these pre-defined settings are implemented as hardwired connections on the component side of the PCB; meaning that one cannot cut these connections once when the components (jumpers) are installed on the PCB. In the Schneiderware Nachlese, the author did admit that they shipped fully assembled PCBs without cutting these "hidden" connections underneath of the jumpers. Aside from that, the PCB and the (original) schematic haven't been too clear about whether the 4-pin jumpers should connect/disconnect adjacent 2 pins in horizontal or in vertical direction.

Pictures

  • V/24 Schematic

  • V/24 (component side)

  • V/24 (solder side)