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Found on the Osborne 1 luggable computer, released by Osborne Computer Corporation in 1981. This pinout came from the Osborne 1 Technical Manual, and I have had a quick look at the PCB to check it.




 

Pin
Number
Pin
Name
Description
1 GND System ground/shielding
2 A4 Row/address line
3 A0 Row/address line
4 A3 Row/address line
5 A6 Row/address line
6 A2 Row/address line
7 A5 Row/address line
8 A1 Row/address line
9 A7 Row/address line
10 D0 Column/data line
11 D1 Column/data line
12 D2 Column/data line
13 D3 Column/data line
14 D4 Column/data line
15 D5 Column/data line
16 D6 Column/data line
17 D7 Column/data line
18 NC Exists in cable, not connected at either end
19 +12V Connected on PCB, not in cable
20 GND System ground/shielding

Pin 1 is towards the top-right when looking at the front of the computer in the usual fashion. On the later '1a' model which I have, the plug on the coiled keyboard cable actually has 24 holes but the outer 4 do not mate with pins (it's not quite the same plug you find on a ribbon cable).

The Osborne 1 keyboard contains no electronics and does not require a power supply. The row and column lines connect directly to a matrix of keys. I believe that to read a row, the address is selected such that exactly one of the row outputs is driven low. Any pressed keys in that row will cause a zero to be read on the respective column line, while other column lines will be pulled up.

Pins 2-9 are driven by the system address bus through open-collector inverters. Pins 10-17 are pulled up to the system +5V supply by a 3.3K resistor pack, and buffered onto the system data bus when the processor reads the keyboard.

Pin 19 can be connected to the system +12V supply through J6 (a 2-pin link, open on my Rev. D PCB) and R21 (22 ohms).

I'm intending to build a PS/2 keyboard adapter using an ATtiny and a bunch of 74LS374's, as my keyboard was busted when I got it (eBay bargain).

Keyboard matrix layout
  D0 D1 D2 D3 D4 D5 D6 D7
A0 Esc Tab Ctrl   Shift Return ' [ ]
A1 1 ! 2 @ 3 £ 4 $ 5 % 6 ^ 7 & 8 *
A5 Up Left 0 ) Space . > P O 9 (
A2 Q W E R T Y U I
A3 A S D F G H J K
A4 Z X C V B N M , <
A6 Right Down - _ / ? ; : \ | L = +
A7       Lock        




 

20 pin IDC male connector layout
20 pin IDC male connector
at the computer
20 pin IDC female connector layout
20 pin IDC female connector
at the keyboard cable
According to 2 reports in our database (2 positive and 0 negative) this pinout should be correct.

Is this pinout
Source(s) of this and additional information: Osborne 1 Technical Manual
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