The ASCII Keyboard

Acorn System Keyboard Bare PCBAcorn System Keyboard Cased

"The Acorn keyboard uses a high quality 62 key mechanism for professional computer input applications. The key mechanism is mounted on a 355 x 150mm PCB which also carries circuitry to scan and encode the keys producing the ASCII code for any key which is pressed. The keyboard encoder circuit has a 2-key rollover feature enabling fast typing speeds. ASCII is a 7-bit code for up to 128 characters and the keyboard outputs this code in parallel on seven signal lines at TTL level (TTL logic 0, +5V logic 1). Also output is a strobe signal which may be selected to be positive or negative going to indicate that a key is being pressed. A single +5V supply at 80mA is required to run the keyboard. All connections to the keyboard are normally via a 20-way flat ribbon cable which connects straight to Acorn computer systems.

On the keyboard are some special function keys. Two of them connect straight to the output connector on individual signal lines giving a logic 0 when pressed. One may be used to reset the computer (break) and the other can connect to an input port on the computer for examination by the users own software. Two other keys, control and shift, change the character set produced by the keyboard encoder circuit to give ASCII control characters and upper/lower case selection. There is a shift lock key and another key locks the keyboard into a TTY Caps mode (TeleType Capitals) where the shift key works as usual for numbers and symbols but only capital alphabetic characters are produced. This is useful when programming in languages like BASIC where lower case alphabetic characters are illegal. The output signal lines always carry the code for the last key to be pressed even if the key has been released and a repeat key causes the strobe to start pulsing giving repeated codes for the same key to the computer. An auto repeat feature starts the repeat circuitry automatically if the key is held down for more than one second. Three LEDs on the circuit board indicate TTY Caps mode, shift mode and power on.

The keyboard can be supplied in a stylish injection moulded plastic case if required.

The keyboard is only available assembled and tested."




200.0Acorn System Keyboard PCB Issue 213 Issue 2 [3 System 4]

Acorn System Keyboard PCB Issue 2

200.013 Issue 3 [3 System 3]

Acorn System Keyboard Issue 3Acorn System Keyboard Issue 3

Acorn System Keyboard PCB Issue 3Acorn System Keyboard PCB Issue 3

 200.013 Issue 3 [3 System 5]

Acorn System Keyboard Issue 3

Acorn System Keyboard PCB Issue 3Acorn System Keyboard PCB Issue 3

Data Sheets:


I have made two replica versions of this keyboard details of which can be found here:


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