The Keyboard, Display & Cassette Interface Board

Acorn System 1 PhotoKeyboard, Display & Cassette Interface Board Photo

"The upper Eurocard of the System 1 is available without the keypad and display when it performs as a Cassette Interface card in System 2. It may also be added to Systems 3, 4 and 5 if desired. The Computer Users Tape Standard (CUTS) frequency modulates data on to a standard audio cassette recorder with a two tone system in which 2.4KHz represents a logic 1 and 1.2KHz a logic 0." 

If the Keyboard, Display & Cassette Interface Board is fitted in card frame as a Cassette Interface Board then a number of signal lines need to be wired to the 64-way connector.  The System 2 Technical Manual suggests using B-side pins 19, 20 and 21 for CASIN, CASOUT and NHITONE respectively whilst the 6502A CPU Board uses pins 3, 4 and 5.

B19 and B20 are not allocated on any other boards however B21 carries a 1MHz clock on the 6502A CPU Boards so I have opted for using B19, B20 and B23 as follows:

You also need to wire O2 on A29 to IC1 pin 1.

Of course you then need to make the same connections on the CPU Board:

I haven't modified a 6502A CPU Board as they are unlikely to be used with a cassette interface, in any case I don't think the cassette routines in COS would work as the 6502A uses a 6522 PIA rather than an 8154.


Note: all 3 versions of the schematic have an error at IC2: pins 5 and 6 are transposed i.e. IC2/pin 5 should go to IC3/pin 6 and IC2/pin 6 should go to IC3/pin 8.




200.001 Issue unknown [0] 

Keyboard, Display & Cassette Interface Board Top PhotoKeyboard, Display & Cassette Interface Board Track Side


200.001 Issue unknown [7] 

This example was probably intended as just a Cassette Interface, perhaps for a System 2, as the display/keyboard and 7445 driver have not been fitted.

Cassette Interface Board Top Photo


Replica Board:

trev_ham has made a replica of this board details of which can be found here:


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