
Rev.1.00
REJ03B0212-0100
Apr 2, 2007
Page 36 of 117
3803 Group (Spec.L)
(4) Pulse period measurement mode
Mode selection
This mode can be selected by setting “010” to the timer Z
operating mode bits (bits 2 to 0) and setting “0” to the
timer/event counter mode switch bit (b7) of the timer Z mode
register (address 002A
16
Count source selection
In high- or middle-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64,
1/128, 1/256, 1/512 or 1/1024 of f(X
IN
); or f(X
CIN
) can be
selected as the count source.
In low-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256,
1/512 or 1/1024 of f(X
CIN
); or f(X
CIN
) can be selected as the
count source.
Interrupt
The interrupt at an underflow is the same as the timer mode’s.
When the pulse period measurement is completed, the
INT
4
/CNTR
2
interrupt request bit (bit 5) of the interrupt request
register 2 (address 003D
16
) is set to “1”.
Explanation of operation
The cycle of the pulse which is input from the CNTR
2
pin is
measured. When the CNTR
2
active edge switch bit (bit 5) of the
timer Z mode register (address 002A
16
) is “0”, the timer counts
during the term from one falling edge of CNTR
2
pin input to the
next falling edge. When it is “1”, the timer counts during the
term from one rising edge input to the next rising edge input.
When the valid edge of measurement completion/start is
detected, the 1’s complement of the timer value is written to the
timer latch and “FFFF
16
” is set to the timer.
Furthermore when the timer underflows, the timer Z interrupt
request occurs and “FFFF
16
” is set to the timer. When reading
the timer Z, the value of the timer latch (measured value) is read.
The measured value is retained until the next measurement
completion.
Precautions
Set the double-function port of CNTR
2
pin and port P4
7
to input
in this mode.
A read-out of timer value is impossible in this mode. The timer
can be written to only during timer stop (no measurement of
pulse period).
Since the timer latch in this mode is specialized for the read-out
of measured values, do not perform any write operation during
measurement.
“FFFF
16
” is set to the timer when the timer underflows or when
the valid edge of measurement start/completion is detected.
Consequently, the timer value at start of pulse period
measurement depends on the timer value just before
measurement start.
Figure 32 shows the timing chart of the pulse period
measurement mode.
(5) Pulse width measurement mode
Mode selection
This mode can be selected by setting “011” to the timer Z
operating mode bits (bits 2 to 0) and setting “0” to the
timer/event counter mode switch bit (b7) of the timer Z mode
register (address 002A
16
).
Count source selection
In high- or middle-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64,
1/128, 1/256, 1/512 or 1/1024 of f(X
IN
); or f(X
CIN
) can be
selected as the count source.
In low-speed mode, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256,
1/512 or 1/1024 of f(X
CIN
); or f(X
CIN
) can be selected as the
count source.
Interrupt
The interrupt at an underflow is the same as the timer mode’s.
When the pulse widths measurement is completed, the
INT
4
/CNTR
2
interrupt request bit (bit 5) of the interrupt request
register 2 (address 003D
16
) is set to “1”.
Explanation of operation
The pulse width which is input from the CNTR
2
pin is measured.
When the CNTR
2
active edge switch bit (bit 5) of the timer Z
mode register (address 002A
16
) is “0”, the timer counts during
the term from one rising edge input to the next falling edge input
(“H” term). When it is “1”, the timer counts during the term from
one falling edge of CNTR
2
pin input to the next rising edge of
input (“L” term).
When the valid edge of measurement completion is detected, the
1’s complement of the timer value is written to the timer latch.
When the valid edge of measurement completion/start is
detected, “FFFF
16
” is set to the timer.
When the timer Z underflows, the timer Z interrupt occurs and
“FFFF
16
” is set to the timer Z. When reading the timer Z, the
value of the timer latch (measured value) is read. The measured
value is retained until the next measurement completion.
Precautions
Set the double-function port of CNTR
2
pin and port P4
7
to input
in this mode.
A read-out of timer value is impossible in this mode. The timer
can be written to only during timer stop (no measurement of
pulse widths).
Since the timer latch in this mode is specialized for the read-out
of measured values, do not perform any write operation during
measurement.
“FFFF
16
” is set to the timer when the timer underflows or when
the valid edge of measurement start/completion is detected.
Consequently, the timer value at start of pulse width
measurement depends on the timer value just before
measurement start.
Figure 33 shows the timing chart of the pulse width measurement
mode.