4501 datasheet(29/116 Pages) RENESAS

29 / 116 page

4501 Group

Rev.3.01

2005.02.07

page 29 of 112

REJ03B0104-0301

(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.

Fig. 23 Count timing diagram at 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.

0316

0216

0116

0016

FF16

FE16

CNTR input

Timer 2 count

Timer 2 interrupt

request flag

(T2F)

(Note)

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

• Timer 1 and timer 2 count start timing and count time when op-

eration starts

Count starts from the first rising edge of the count source (2) af-

ter timer 1 and timer 2 operations start (1).

Time to first underflow (3) is shorter (for up to 1 period of the

count source) than time among next underflow (4) by the timing

to start the timer and count source operations after count starts.

When selecting CNTR input as the count source of timer 2, timer

2 operates synchronizing with the falling edge of CNTR input.

Fig. 24 Timer count start timing and count time when opera-

tion starts (T1, T2)

(1) Timer

Count Source

Timer Value

Timer Underflow

Signal

032

103

Count Source

(CNTR input)

(2)

(3)

(4)

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