Computer Interfacing

Computer interfacing

Any desired code can be generated, for example the ASCII

code referred to, by storing the codes in a ROM and us-

ing the binary outputs from the scanned keyboard, not

as the actual codes themselves, but as addresses in the

ROM where the actual codes are found. The block dia-

gram of Figure 2.3 shows the arrangement for a scanning

keyboard which uses codes stored in a ROM, each out-

put code from the ROM being held in a set of latches

before being passed to the computer.

Scanning

encoder

&

keyboard

tt

-o +V

CTRL

ROM

code

converter

tt

Output

latches

Leading edge

(key down)

detector

K

ASCII

-S code

output

Keyboard

strobe

Figur ...