Matrix keyboard

[civictypeR]

Hey guys ,
just asking , i have a picture of a matrix keyboard but i do not know how does the diode help in producing different outputs when i press a certain key in . This is the schematic diagram of the matrix keyboard **broken link removed**

Thanks guys .

 

[ericgibbs]

hi,

I posted your diagram.........
and link: **broken link removed**

Its a technique, IIRC called Charlie Plexing, where pins are programmed as inputs or outputs to provide a scanning code.
The diodes are sometimes called 'steering' or blocking diodes. Basically they only allow the 'high' pins output current to flow
in the required path and block any 'sneak' paths to other pins.

Do you follow that OK.?