A4.8051 Communication Protocols:UART, RS232
Contents
UART Serial communication using 8051
We have covered the basics of timers in the previous tutorial, with that we can see how can a microcontroller communicate with a computer serially.
There are two ways to connect a microcontroller to a computer.
- Using RS232 protocol to the legacy serial port.
- Using a USB to serial convertor.
From microcontroller programming point of view, there is fundamentally no difference.
8051 UART Registers
SBUFF: Serial buffer register
| SBUFF | |||||||
|---|---|---|---|---|---|---|---|
| D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |
SCON: Serial Control Register
| SCON | |||||||
|---|---|---|---|---|---|---|---|
| D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |
| SM0 | SM1 | SM2 | REN | TB8 | RB8 | TI | RI |
| SM0 | SM1 | Operation | Description | Baud Rate Source |
|---|---|---|---|---|
| 0 | 0 | Mode 0 | 8bit ShiftReg | 1/12 the quartz frequency |
| 0 | 1 | Mode 1 | 8 bit UART | Determined by the timer 1 |
| 1 | 0 | Mode 2 | 9 bit UART | 1/32 the quartz frequency |
| 1 | 1 | Mode 0 | 9 bit UART | Determined by the timer 1 |
| Bit | Name | |
|---|---|---|
| 7 | ||
| 6 | ||
| 5 | ||
| 4 | ||
| 3 | ||
| 2 | ||
| 1 | ||
| 0 |