ADuC812

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

 

Register

SFR Address

89H

Power-On Default Value

00H

Bit Addressable

No

Gate

C/T

M1

M0

Gate

C/T

M1

M0

 

 

 

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.

 

 

 

 

 

–30–

REV. B

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Analog Devices ADuC812 manual TMOD, Tcon, T2CON