4583 Datasheet, PDF (37/153 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.
(7) Period measurement function (Timer 1,
period measurement circuit)
Timer 1 has the period measurement circuit which performs timer
count operation synchronizing with the one cycle of the signal di-
vided by 16 of an on-chip oscillator, D6/CNTR0 pin input, or P30/
INT0 pin input (one cycle, “H”, or “L” pulse width at the case of a
P30/INT0 pin input).
When the target signal for period measurement is set by bits 0
and 1 of register W5, a period measurement circuit is started by
setting the bit 2 of register W5 to “1”.
Then, if a XIN input is set as the count source of a timer 1 and the
bit 2 of register W1 is set to “1”, timer 1 starts operation.
Timer 1 starts operation synchronizing with the falling edge of the
target signal for period measurement, and stops count operation
synchronizing with the next falling edge (one-period generation
circuit).
When selecting D6/CNTR0 pin input as target signal for period
measurement, the period measurement synchronous edge can
be changed into a rising edge by setting the bit 2 of register W6
to “1”.
When selecting P30/INT0 pin input as target signal for period
measurement, period measurement synchronous edge can be
changed into a rising edge by setting the bit 2 of register I1 to “1”.
A timer 1 interrupt request flag (T1F) is set to “1” after completing
measurement operation.
When a period measurement circuit is set to be operating, timer
1 interrupt request flag (T1F) is not set by timer 1 underflow sig-
nal, but turns into a flag which detects the completion of period
measurement.
In addition, a timer 1 underflow signal can be used as timer 2
count source.
Once period measurement operation is completed, even if period
measurement valid edge is input next, timer 1 is in a stop state
and measurement data is held.
When a period measurement circuit is used again, stop a period
measurement circuit at once by setting the bit 2 of register W5 to
“0”, and change a period measurement circuit into a state of op-
eration by setting the bit 2 of register W5 to “1” again.
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 27➀) 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 27➁).
Also, set the NOP instruction for the case when a skip is per-
formed with the SNZT1 instruction (refer to Figure 27➂).
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. 27 Period measurement circuit program example
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.)
(8) Pulse width measurement function (timer
1, period measurement circuit)
A period measurement circuit can measure “H” pulse width (from
rising to falling) or “L” pulse width (from falling to rising) of P30/
INT0 pin input (pulse width measurement function) when the fol-
lowing is set;
• Set the bit 0 of register W5 to “0”, and set a bit 1 to “1” (target
for period measurement circuit: 30/INT0 pin input).
• Set the bit 1 of register I1 to “1” (INT0 pin edge detection circuit:
both edges detection)
The measurement pulse width (“H” or “L”) is decided by the pe-
riod measurement circuit and the P30/INT0 pin input level at the
start time of timer operation.
At the time of the start of a period measurement circuit and timer
operation, “L” pulse width (from falling to rising) when the input
level of P30/INT0 pin is “H” or “H” pulse width (from rising to fall-
ing) when its level is “L” is measured.
When the input of P30/INT0 pin is selected as the target for mea-
surement, set the bit 3 of register I1 to “1”, and set the input of
INT0 pin to be enabled.
Rev.3.00 Aug 06, 2004 page 37 of 151
REJ03B0009-0300Z