IS80C51 Datasheet, PDF (13/43 Pages) Integrated Silicon Solution, Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER

IS80C51
IS80C31
ISSI ^®
TMOD:
Timer/Counter Mode Control Register.
Not Bit Addressable.
Timer 1
GATE C/T M1 M0
Timer 0
GATE C/T 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).
C/T Timer or Counter selector. Cleared for Timer
operation (input from internal system clock). Set for
Counter operation (input from Tx input pin).
M1 Mode selector bit.⁽¹⁾
M0 Mode selector bit.⁽¹⁾
Note 1:
M1 M0 Operating mode
0 0 Mode 0. (13-bit Timer)
0 1 Mode 1. (16-bit Timer/Counter)
1 0 Mode 2. (8-bit auto-load Timer/Counter)
1 1 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.)
1 1 Mode 3. (Timer/Counter 1 stopped).
SCON:
Serial Port Control Register. Bit Addressable.
7
65
4
3
2
10
SM0 SM1 SM2 REN TB8 RB8 TI RI
Register Description:
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.
TI SCON.1 Transmit interrupt flag. Set by hardware
at the end of the 8th bit time in mode 0,
or at the beginning of the stop bit in the
other modes. Must be cleared by
software.
RI SCON.0 Receive interrupt flag. Set by hardware
at the end of the 8th 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:
SM0 SM1 MODE Description Baud rate
0 0 0 Shift register Fosc/12
0 1 1 8-bit UART Variable
1 0 2 9-bit UART Fosc/64 or Fosc/32
1 1 3 9-bit UART Variable
Integrated Silicon Solution, Inc. — 1-800-379-4774
13
MC003-1D
11/19/98