4583 Datasheet, PDF (39/153 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4583 Group
PRELIMINARY
Notice: This is not a final specification.
Some parametric limits are subject to change.
(13) Timer interrupt request flags
(T1F, T2F, T3F, T4F)
Each timer interrupt request flag is set to “1” when each timer
underflows. The state of these flags can be examined with the skip
instructions (SNZT1, SNZT2, SNZT3, SNZT4).
Use the interrupt control register V1, V2 to select an interrupt or a
skip instruction.
An interrupt request flag is cleared to “0” when an interrupt occurs
or when the next instruction is skipped with a skip instruction. The
timer 1 interrupt request flag (T1F) is not set by the timer 1 under-
flow signal, it is the flag for detecting the completion of period
measurement.
(14) 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 and 4 counting to change its count source.
• Period measurement function
When a period measurement circuit is used, clear bit 0 of regis-
ter I1 to “0”, and set a timer 1 count start synchronous circuit to
be “not selected”.
Start timer operation immediately after operation of a period
measurement circuit is started.
When the target edge for measurement is input until timer opera-
tion is started from the operation of period measurement circuit is
started, the count operation is not executed until the timer opera-
tion becomes valid. Accordingly, be careful of count data.
When data is read from timer, stop the timer and clear bit 2 of
register W5 to “0” to stop the period measurement circuit, and
then execute the data read instruction.
Depending on the state of timer 1, the timer 1 interrupt request
flag (T1F) may be set to “1” when the period measurement cir-
cuit is stopped by clearing bit 2 of register W5 to “0”. In order to
avoid the occurrence of an unexpected interrupt, clear the bit 2 of
register V1 to “0” (refer to Figure 28➀) and then, stop the bit 2 of
register W5 to “0” to stop the period measurement circuit.
In addition, execute the SNZT1 instruction to clear the T1F flag
after executing at least one instruction (refer to Figure 28➁).
Also, set the NOP instruction for the case when a skip is per-
formed with the SNZT1 instruction (refer to Figure 28➂).
• 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 or 4 counting and then execute the data write
instruction (T1AB, T2AB, T3AB, T4AB) 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 at the use
of PWM output function.
When “H” interval extension function of the PWM signal is set to
be “valid”, set “1” or more to reload register R4H.
• Timer input/output pin
When the PWM signal is output from C/CNTR1 pin, set the out-
put latch of port C to “0”.
LA 0
TV1A
LA 0
TW5A
NOP
SNZT1
NOP
; (✕0✕✕2)
; The SNZT1 instruction is valid ........ ➀
; (✕0✕✕2)
; Period measurement circuit stop
........................................................... ➁
; The SNZT1 instruction is executed
(T1F flag cleared)
........................................................... ➂
✕ : these bits are not used here.
Fig. 28 Period measurement circuit program example
While a period measurement circuit is operating, the timer 1 in-
terrupt request flag (T1F) is not set by the timer 1 underflow
signal, it is the flag for detecting the completion of period mea-
surement.
When a period measurement circuit is used, select the suffi-
ciently higher-speed frequency than the signal for measurement
for the count source of a timer 1.
When the target signal for period measurement is D6/CNTR0 pin
input, do not select D6/CNTR0 pin input as timer 1 count source.
(The XIN input is recommended as timer 1 count source at the
time of period measurement circuit use.)
When the input of P30/INT0 pin is selected for measurement, set
the bit 3 of a register I1 to “1”, and set the input of INT0 pin to be
enabled.
Rev.3.00 Aug 06, 2004 page 39 of 151
REJ03B0009-0300Z