Servicing Personal Computers, 3rd Edition

52 Servicing Personal Computers

interrupt is generated when a key depression is detected by a return signal appearing on a

column line. Note that special function keys, such as 'Shift' and 'Control', do not form part of

the matrix. These, higher priority, keys are treated separately as direct inputs to port A.

Serial input and output

Parallel data transfer is primarily suited to high-speed operation over relatively short distances,

a typical example being the linking of a microcomputer to an adjacent dot matrix printer.

There are, however, a number of applications in which parallel data transfer is inappropriate,

the most common example bein ...