SM89516B datasheet(34/49 Pages) SYNCMOS

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SM89516B

8-Bit Micro-controller

64KB Flash

& 1KB RAM embedded

Specifications subject to change without notice contact your sales representatives for the most recent information.

ISSFD-M087

Ver D SM89516B 08/07/2015

- 34 -

Serial interface – UART

The serial buffer consists of two separate registers, a transmit buffer and a receive buffer.

Writing data to the Special Function Register SBUF sets this data in serial output buffer and starts the transmission.

Reading from the SBUF reads data from the serial receive buffer. The serial port can simultaneously transmit and

receive data. It can also buffer 1 byte at receive, which prevents the receive data from being lost if the CPU reads

the first byte before transmission of the second byte is completed.

Mnemonic

Description

Dir.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

RST

Serial interface

PCON

Power Control

87H

SMOD

GF1

GF0

IDLE

00H

SCON

Serial Port

Control Register

98H

SM0

SM1

SM2

REN

TB8

RB8

00H

SBUF

Serial Port Data

Buffer

99H

SBUF[7:0]

00H

Mnemonic: SCON

Address: 98h

Reset

SM0

SM1

SM2

REN

TB8

RB8

00H

SM0, SM1: Serial Port mode selection.

SM0

SM1

Mode

The 4 modes in UART, Mode 0 ~ 3, are explained later.

SM2: Enables multiprocessor communication feature.

REN: If set, enables serial reception. Cleared by software to disable reception.

TB8: The 9th transmitted data bit in modes 2 and 3. Set or cleared by the CPU depending on

the function it performs such as parity check, multiprocessor communication etc.

RB8: In modes 2 and 3, it is the 9th data bit received. In mode 1, if SM2 is 0, RB8 is the stop

bit. In mode 0, this bit is not used. Must be cleared by software.

TI: Transmit interrupt flag, set by hardware after completion of a serial transfer. Must be

cleared by software.

RI: Receive interrupt flag, set by hardware after completion of a serial reception. Must be

cleared by software.

8.1

Serial interface

The Serial Interface can operate in the following 4 modes:

SM0

SM1

Mode

Description

Board Rate

Shift register

Fosc/12

8-bit UART

Variable

9-bit UART

Fosc/32 or Fosc/64

9-bit UART

Variable

Here Fosc is the crystal or oscillator frequency.

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