The earliest typewriters used a purely mechanical link between the keyboard and the printer. They were slow, inefficient, and “dumb”. Today’s typewriters have spliced intelligence into the linkage, and they are fast, flexible, and “smart”. First, however, we must become familiar with a few basic principles of parallel input /output.
1) Synchronous vs asynchronous timing.
2) Requirements of asynchronous transmission.
3) Handshaking.
4) Programmed I/O vs interrupt I/O.
5) Memory-mapped I/O vs isolated I/O.
6) The IBM PC parallel port.
Second, in W. Ditch book, 4 – Microprocessor Support ICs: a] Parallel interface ICs, b] Handshaking, c] Serial data transfer (software & hardware), d] RS 232 serial interface, e] Counting and time measurement using hardware.
Practical exercises: i] Centronic printer interface, ii] Parallel computer interface, iii] Local area network, iv] Parity generation and checking, v] Shift register, vi] Running light displays, vii] Software serial interface, viii] RS 232 investigation, ix] Software real time clock, x] Digital frequency meter.
