4554 Datasheet, PDF (40/138 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4554 Group
(11) Count start synchronization circuit (timer 1,
timer 3)
Timer 1 and timer 3 have the count start synchronous circuit which
synchronizes the input of INT0 pin and INT1 pin, and can start the
timer count operation.
Timer 1 count start synchronous circuit function is selected by set-
ting the bit 0 of register I1 to “1” and the control by INT0 pin input
can be performed.
Timer 3 count start synchronous circuit function is selected by set-
ting the bit 0 of register I2 to “1” and the control by INT1 pin input
can be performed.
When timer 1 or timer 3 count start synchronous circuit is used, the
count start synchronous circuit is set, the count source is input to
each timer by inputting valid waveform to INT0 pin or INT1 pin.
The valid waveform of INT0 pin or INT1 pin to set the count start
synchronous circuit is the same as the external interrupt activated
condition.
Once set, the count start synchronous circuit is cleared by clearing
the bit I10 or I20 to “0” or reset.
However, when the count auto-stop circuit is selected, the count
start synchronous circuit is cleared (auto-stop) at the timer 1 or
timer 3 underflow.
(12) Count auto-stop circuit (timer 1, timer 3)
Timer 1 has the count auto-stop circuit which is used to stop timer
1 automatically by the timer 1 underflow when the count start syn-
chronous circuit is used.
The count auto-stop cicuit is valid by setting the bit 3 of register W1
to “1”. It is cleared by the timer 1 underflow and the count source to
timer 1 is stopped.
This function is valid only when the timer 1 count start synchronous
circuit is selected.
Timer 3 has the count auto-stop circuit which is used to stop timer
3 automatically by the timer 3 underflow when the count start syn-
chronous circuit is used.
The count auto-stop cicuit is valid by setting the bit 3 of register W3
to “1”. It is cleared by the timer 3 underflow and the count source to
timer 3 is stopped.
This function is valid only when the timer 3 count start synchronous
circuit is selected.
(13) Precautions
Note the following for the use of timers.
• Prescaler
Stop counting and then execute the TABPS instruction to read
from prescaler data.
Stop counting and then execute the TPSAB instruction to set
prescaler data.
• Timer count source
Stop timer 1, 2, 3, 4 and LC counting to change its count source.
• Reading the count value
Stop timer 1, 2, 3 or 4 counting and then execute the data read
instruction (TAB1, TAB2, TAB3, TAB4) to read its data.
• Writing to the timer
Stop timer 1, 2, 3, 4 or LC counting and then execute the data
write instruction (T1AB, T2AB, T3AB, T4AB, TLCA) to write its
data.
• Writing to reload register R1, R3, R4H
When writing data to reload register R1, reload register R3 or re-
load regiser R4H while timer 1, timer 3 or timer 4 is operating,
avoid a timing when timer 1, timer 3 or timer 4 underflows.
• Timer 4
Avoid a timing when timer 4 underflows to stop timer 4.
When “H” interval extension function of the PWM signal is set to
be “valid”, set “1” or more to reload register R4H.
• Timer 5
Stop timer 5 counting to change its count source.
• Timer input/output pin
Set the port C output latch to “0” to output the PWM signal from
C/CNTR pin.
Rev.3.00 Aug 06, 2004 page 40 of 136
REJ03B0043-0300Z