- 2070 Magh · 4 marks
Short note: serial and parallel interface
Short answer
Parallel interface sends all bits of a byte simultaneously on separate lines; it is fast but needs many wires and suits short distances. Serial interface sends bits one after another on one line, needing few wires for long distances but slower. Examples: 8255 PPI and 8251A USART.
Write a short note on serial and parallel interface.
An interface is the circuit that connects the microprocessor to a peripheral. By the way data is sent, it is either parallel or serial.
Parallel interface: all bits of a byte (or word) are sent together on separate lines, one line per bit, plus control (strobe/acknowledge) lines. It is fast and simple, but needs many wires, so it suits short distances (printer, keyboard, ADC). Chip: 8255 PPI.
Serial interface: bits are sent one after another on one line (plus ground, and control lines if needed). A parallel-to-serial shift register (UART/USART) does the conversion. It needs few wires and works over long distance, but is slower. Chip: 8251A USART. Standards: RS-232.
| Point | Parallel | Serial |
|---|---|---|
| Bits per clock | 8 or more | 1 |
| Lines needed | Many (8 data + control) | Few (TxD, RxD, GND) |
| Speed (short distance) | High | Lower |
| Distance | Short (a few metres) | Long |
| Cost of cable | High | Low |
| Crosstalk/noise | More | Less |
| Examples | Centronics printer, 8255 | RS-232, USB, 8251A |
Parallel: P-> D0 D1 D2 D3 D4 D5 D6 D7 -> (8 wires)
Serial : P-> D0 D1 D2 D3 ... D7 (one wire, bit by bit)
✓ Answer checked by Claude Opus 5.5 (high effort)
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