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4501

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

MITSUBISHI MICROCOMPUTERS

4501 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

(8) Timer input/output pin (P12/CNTR pin)

CNTR pin is used to input the timer 2 count source and output the

timer 1 and timer 2 underflow signal divided by 2.

The P12/CNTR pin function can be selected by bit 0 of register W6.

The CNTR output signal can be selected by bit 1 of register W6.

When the CNTR input is selected for timer 2 count source, timer 2

counts the falling waveform of CNTR input.

(9) Precautions

Note the following for the use of timers.

• Prescaler

Stop the prescaler operation to change its frequency dividing ra-

tio.

• Count source

Stop timer 1 or 2 counting to change its count source.

• Reading the count value

Stop timer 1 or 2 counting and then execute the TAB1 or TAB2

instruction to read its data.

• Writing to the timer

Stop timer 1 or 2 counting and then execute the T1AB or T2AB

instruction to write its data.

• Writing to reload register R1

When writing data to reload register R1 while timer 1 is operat-

ing, avoid a timing when timer 1 underflows.

CNTR input

Timer 2 count 0316

0216

0116

0016

(Note)

FF16

FE16

Timer 2 interrupt

request flag

(T2F)

Note: This is an example when “FF16” is set to timer 2 reload register R2L.

Fig. 23 Count timing diagram at CNTR input

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