Computer Interfacing

Computer interfacing

The maximum of 88 keys that can be used with this IC

should be wired on an 11 x 8 key matrix with a single-

pole,

single-throw switch at each crossing. In the standby

state,

with no keys pressed, the ring counters

sequentially address the ROM locations but the absence

of a keyboard strobe pulse indicates that there is no valid

data available.

An application circuit for the 2376 keyboard encoder is

shown in Figure 6.4. When a key is depressed, a path is

completed between one of the outputs of the 8-stage ring

counter (X0-X7) and one of the inputs of the 11-bit com-

parator (Y0-Y10). Shortly after, the comparator sends a

signa ...