4571 Datasheet, PDF (33/126 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

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.
(2)
Count source
Count source
(When falling edge of
CNTR0 input is selected)
Timer 1 value 3 2 1 0 3 2 1 0 3 2
Timer 1 underflow signal
(3)
(4)
(1) Timer start
Fig 33. Timer count start timing and count time when
operation starts
Rev.1.02 May 25, 2007 Page 33 of 124
REJ03B0179-0102