On-Chip Peripheral Components
C513AO
User’s Manual
6-18
05.99
Special Function Register TMOD (Address 89H)
Reset Value: 00H
Bit
Function
GATE
Gating control
When set, Timer/Counter “x” is enabled only while “INT x” pin is high and “TRx”
control bit is set.
When cleared, Timer “x” is enabled whenever “TRx” control bit is set.
C/T
Counter or Timer select bit
Set for Counter operation (input from “Tx” input pin).
Cleared for Timer operation (input from internal system clock).
M1
M0
Mode select bits
GATE
C/T
M1
M0
89H
TMOD
Bit No.
7
6
5
4
3
2
1
0
MSB
LSB
GATE
C/T
M1
M0
Timer 1 Control
Timer 0 Control
M1
M0
Function
0
0
8-bit timer/counter:
“THx” operates as 8-bit timer/counter
“TLx” serves as 5-bit prescaler
0
1
16-bit timer/counter.
“THx” and “TLx” are cascaded; there is no prescaler
1
0
8-bit auto-reload timer/counter.
“THx” holds a value which is to be reloaded into “TLx” each
time it overflows
1
1
Timer 0:
TL0 is an 8-bit timer/counter controlled by the standard
Timer 0 control bits. TH0 is an 8-bit timer only controlled by
Timer 1 control bits.
Timer 1:
Timer/Counter 1 stops