INTERNAL SPECIFICATIONS

4.4.2Special function registers 4.4.2.1 Timer mode register (TMOD)

Name

Address

MSB

 

 

 

 

 

 

 

 

 

 

 

LSB

 

7

 

6

 

5

 

4

3

 

2

 

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TMOD

89H

GATE

 

C/T

 

M1

 

M0

GATE

 

C/T

 

M1

 

M0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit location

Flag

 

 

 

 

 

 

 

Function

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TMOD.0

M0

M1 M0

 

Timer/counter 0 mode setting

 

 

 

 

 

 

 

0

0

 

8-bit timer/counter with 5-bit prescalar

 

 

 

 

 

0

1

 

16-bit timer/counter

 

 

 

 

 

 

 

 

 

1

0

 

8-bit timer/counter with 8-bit auto reloading

 

 

 

TMOD.1

M1

 

 

 

 

 

 

1

1

 

Timer/counter 0 separated into TL0 (8-bit) timer/counter

 

 

 

 

 

and TH0 (8-bit) timer/counter. TF0 is set by TL0 carry,

 

 

 

 

 

and TF1 is set by TH0 carry.

 

 

 

 

 

 

 

 

 

 

 

TMOD.2

C/T

Timer/counter 0 count clock designation control bit.

 

 

 

 

 

XTAL1·2 divided by 12 clock is the input applied to timer/counter 0

 

 

when C/T="0".

 

 

 

 

 

 

 

 

 

 

 

 

 

The external clock applied to the T0 pin is the input applied to

 

 

 

timer/counter 0 when C/T="1".

 

 

 

 

 

 

 

 

 

 

TMOD.3

GATE

When this bit is "0", the TR0 bit of TCON (timer control register) is

 

 

used to control the start and stop of timer/counter 0 counting. If

 

 

this bit is "1", timer/counter 0 starts counting when both the TR0 bit

 

 

of TCON and INT0 pin input signal are "1", and stops counting

 

 

when either is changed to "0".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TMOD.4

M0

M1 M0

 

Timer/counter 1 mode setting

 

 

 

 

 

 

 

0

0

 

8-bit timer/counter with 5-bit prescalar

 

 

 

 

 

0

1

 

16-bit timer/counter

 

 

 

 

 

 

 

 

 

1

0

 

8-bit timer/counter with 8-bit auto reloading

 

 

 

TMOD.5

M1

 

 

 

 

 

 

1

1

 

Timer/counter 1 operation stopped

 

 

 

 

 

 

 

 

 

 

 

TMOD.6

C/T

Timer/counter 1 count clock designation control bit.

 

 

 

 

 

XTAL1·2 divided by 12 clock is the input applied to timer/counter 1

 

 

when C/T="0".

 

 

 

 

 

 

 

 

 

 

 

 

 

The external clock applied to the T1 pin is the input applied to

 

 

 

timer/counter 1 when C/T="1".

 

 

 

 

 

 

 

 

 

 

TMOD.7

GATE

When this bit is "0", the TR1 bit of TCON is used to control the

 

 

start and stop of timer/counter 1 counting.

 

 

 

 

 

 

 

If this bit is "1", timer/counter 1 starts counting when both the TR1

 

 

bit of TCON and INT1 pin input signal are "1", and stops counting

 

 

when either is changed to "0".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Sonic Alert msm85c154hvs, msm83c154s, msm80154s user manual Special function registers 4.4.2.1 Timer mode register Tmod