4571 datasheet(33/126 Pages) RENESAS

33 / 126 page

Rev.1.02

May 25, 2007

Page 33 of 124

REJ03B0179-0102

4571 Group

(11) Precautions

• Prescaler

Stop prescaler counting and then execute the TABPS

instruction to read its data.

Stop prescaler counting and then execute the TPSAB

instruction to write data to prescaler.

Stop prescaler counting to change its count source.

• Timer count source

Stop timer 1, 2 or 3 counting to change its count source.

• Reading the count value

Stop timer 1, 2 or 3 counting and then execute the TAB1,

TAB2 or TAB3 instruction to read its data.

• Writing to the timer

Stop timer 1, 2 or 3 counting and then execute the T1AB,

T2AB, T3AB or T3R3L instruction to write data to timer.

• Writing to reload register

In order to write a data to the reload register R1 while the timer

1 is operating, execute the TR1AB instruction except a timing

of the timer 1 underflow.

In order to write a data to the reload register R3H while the

timer 3 is operating, execute the T3HAB instruction except a

timing of the timer 3 underflow.

• PWM signal

If the timer 3 count stop timing and the timer 3 underflow

timing overlap during output of the PWM signal, a hazard may

occur in the PWM output waveform.

When “H” interval expansion function of the PWM signal is

used, set “1” or more to reload register R3H.

Set the port C output latch to “0” to output the PWM signal

from C/CNTR1 pin.

• Prescaler, timer 1, timer 2 and timer 3 count start timing and

count time when operation starts

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

Figure 33 after prescaler and timer operations start (1) in

Figure 33.

Time to first underflow (3) in Figure 33 is shorter (for up to 1

period of the count source) than time among next underflow

(4) in Figure 33 by the timing to start the timer and count

source operations after count starts.

When selecting CNTR0 input as the count source of timer 1,

timer 1 operates synchronizing with the count edge (falling

edge or rising edge) of CNTR0 input selected by software.

Fig 33. Timer count start timing and count time when

operation starts

Count source

(3)

(4)

(1) Timer start

(2)

Count source

(When falling edge of

CNTR0 input is selected)

Timer 1 value

Timer 1 underflow signal

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