89C52 datasheet(13/50 Pages) ISSI

13 / 50 page

IS89C52

Integrated Silicon Solution, Inc. — 1-800-379-4774

MC013-1C

11/21/98

ISSI®

TMOD:

Timer/Counter Mode Control Register.

Not Bit Addressable.

Timer 1

Timer 0

GATE C/

TTTTT M1 M0

GATE

TTTTT M1 M0

GATE When TRx (in TCON) is set and GATE=1, TIMER/

COUNTERx will run only while

INTx pin is high

(hardware control). When GATE=0, TIMER/

COUNTERx will run only while TRx=1 (software

control).

Timer or Counter selector. Cleared for Timer

operation (input from internal system clock). Set

for Counter operation (input from Tx input pin).

Mode selector bit.(1)

Note 1:

Operating Mode

Mode 0. (13-bit Timer)

Mode 1. (16-bit Timer/Counter)

Mode 2. (8-bit auto-load Timer/Counter)

Mode 3. (Splits Timer 0 into TL0 and

TH0. TL0 is an 8-bit Timer/Counter

controller by the standard Timer 0

control bits. TH0 is an 8-bit Timer and

is controlled by Timer 1 control bits.)

Mode 3. (Timer/Counter 1 stopped).

SCON:

Serial Port Control Register. Bit Addressable.

54321

SM0

SM1

SM2

REN

TB8

RB8

SM0

SCON.7

Serial port mode specifier.(1)

SM1

SCON.6

Serial port mode specifier.(1)

SM2

SCON.5

Enable the multiprocessor com-

munication feature in mode 2 and 3. In

mode 2 or 3, if SM2 is set to 1 then RI

will not be activated if the received 9th

data bit (RB8) is 0. In mode 1, if SM2=1

then RI will not be activated if valid stop

bit was not received. In mode 0, SM2

should be 0.

REN SCON.4

Set/Cleared by software to Enable/

Disable reception.

TB8

SCON.3

The 9th bit that will be transmitted in

mode 2 and 3. Set/Cleared by software.

RB8

SCON.2

In modes 2 and 3, RB8 is the 9th data

bit that was received. In mode 1, if

SM2=0, RB8 is the stop bit that was

received. In mode 0, RB8 is not used.

SCON.1

Transmit interrupt flag. Set by hardware

at the end of the eighth bit time in mode

0, or at the beginning of the stop bit in

the other modes. Must be cleared by

software.

SCON.0

Receive interrupt flag. Set by hardware

at the end of the eighth bit time in mode

0, or halfway through the stop bit time

in the other modes (except see SM2).

Must be cleared by software.

Note 1:

SM0

SM1 MODE

Description

Baud Rate

Shift register

Fosc/12

8-bit UART

Variable

9-bit UART

Fosc/64 or

Fosc/32

9-bit UART

Variable

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