Inc. Computer Hardware User Manual

REV. B

ADuC812

–30–

User configuration and control of all Timer operating modes is

achieved via three SFRs, namely:

TMOD, TCON: Control and configuration for

Timers 0 and 1.

T2CON: Control and configuration for

Timer 2.

TMOD Timer/Counter 0 and 1 Mode

SFR Address 89H

Power-On Default Value 00H

Bit Addressable No

etaGT/C1M0MetaGT/C1M0M

Table XVI. TMOD SFR Bit Designations

Bit Name Description

7 Gate Timer 1 Gating Control.

Set by software to enable timer/counter 1 only while INT1 pin is high and TR1 control bit is set.

Cleared by software to enable timer 1 whenever TR1 control bit is set.

6 C/T Timer 1 Timer or Counter Select Bit.

Set by software to select counter operation (input from T1 pin).

Cleared by software to select timer operation (input from internal system clock).

5 M1 Timer 1 Mode Select Bit 1 (Used with M0 Bit).

4 M0 Timer 1 Mode Select Bit 0.

M1 M0

0 0 TH1 operates as an 8-bit timer/counter. TL1 serves as 5-bit prescaler.

0 1 16-Bit Timer/Counter. TH1 and TL1 are cascaded; there is no prescaler.

1 0 8-Bit Auto-Reload Timer/Counter. TH1 holds a value which is to be

reloaded into TL1 each time it overflows.

1 1 Timer/Counter 1 Stopped.

3 Gate Timer 0 Gating Control.

Set by software to enable timer/counter 0 only while INT0 pin is high and TR0 control bit is set.

Cleared by software to enable Timer 0 whenever TR0 control bit is set.

2 C/T Timer 0 Timer or Counter Select Bit.

Set by software to select counter operation (input from T0 pin).

Cleared by software to select timer operation (input from internal system clock).

1 M1 Timer 0 Mode Select Bit 1.

0 M0 Timer 0 Mode Select Bit 0.

M1 M0

0 0 TH0 operates as an 8-bit timer/counter. TL0 serves as 5-bit prescaler.

0 1 16-Bit Timer/Counter. TH0 and TL0 are cascaded; there is no

prescaler

1 0 8-Bit Auto-Reload Timer/Counter. TH0 holds a value which is to

be reloaded into TL0 each time it overflows.

1 1 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.