Checks if a PC-AT keyboard is connected to the datasette port. You can use this program while building your PC-AT keyboard interface. The interface is very simple, you only need the connectors and some wire. Here, I introduce the information to build the type I interface:

parts list
. AT keyboard female connector. It has five ordered pin-holes. . Datasette port connector. If you can't find, half of an user port conn is Ok. . Some wire and a soldering iron...

front face views of the port and connector:

Keyboard Connector:

      /     \
     /       \
   3 Io     oI 1
     \ o   o / 
    5 \  o  / 4

Datasette Port:

   A B C D E F
   - -I- - - -

And the connections:


    D,E--1     clock line (D is used as an interrupt source)

      F--2     data line

That's all for the hardware.

Scancode data from the keyboard is read by this interface using $dc0d and $01. 4th bit of the $dc0d is triggered every fall of the clock line (1). And 11bit long data is get by reading the data line (2). Also it should be known that, the keyboard is suspended unless the clock line is in the high voltage state.

So, this keyb-check program tests interface and the AT keyboard.

Ilker Ficicilar