C509-L_97 SIEMENS [Siemens Semiconductor Group], C509-L_97 Datasheet - Page 99

• Manufacturer Part Number: C509-L_97
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

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. 89 H )
Bit
GATE
C/T
M1
M0
Semiconductor Group
Bit No.
89 H
GATE
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
MSB
M1
0
0
1
1
7
Timer 1 Control
C/T
M0
0
1
0
1
6
M1
Operating mode
8-bit timer/counter
16-bit timer/counter
8-bit auto-reload timer/counter
Timer 0 : TL0 is an 8-bit timer/counter controlled by the
Timer 1 : Timer/counter 1 stops
5
M0
standard timer 0 control bits. TH0 is an 8-bit timer
only controlled by timer 1 control bits.
4
6-21
GATE
3
On-Chip Peripheral Components
Timer 0 Control
C/T
2
M1
1
LSB
M0
0
Reset Value : 00 H
TMOD
1997-10-01
C509-L