C509-L_97 Datasheet, PDF (99/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C509-L
Special function register TMOD is used for mode select, gating, and counter/timer select purposes.
The lower 4 bits control timer 0 and the upper 4 bits control timer 1.
Special Function Register TMOD (Address. 89H)
Reset Value : 00H
MSB
LSB
Bit No. 7
6
5
4
3
2
1
0
89H GATE C/T M1 M0 GATE C/T M1 M0 TMOD
Timer 1 Control
Timer 0 Control
Bit
GATE
C/T
M1
M0
Function
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.
Counter or timer select bit
Set for counter operation (input from “Tx” input pin).
Cleared for timer operation (input from internal system clock).
Operating mode select bits
M1 M0 Operating mode
0
0
8-bit timer/counter
0
1
16-bit timer/counter
1
0
8-bit auto-reload timer/counter
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
Semiconductor Group
6-21
1997-10-01