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3874 Group User’s Manual
HARDWARE
FUNCTIONAL DESCRIPTION
TIMERS
The 3874 group has five timers: timer X, timer Y, timer 1, timer 2,
and timer 3. Timer X and timer Y are 16-bit timers, and timer 1,
timer 2, and timer 3 are 8-bit timers.
All timers are down count timers. When the timer reaches “0016” or
“000016”, an underflow occurs at the next count pulse and the cor-
responding timer latch is reloaded into the timer and the count is
continued. When a timer underflows, the interrupt request bit cor-
responding to that timer is set to “1”.
Read and write operation on 16-bit timer must be performed for
both high and low-order bytes. When reading a 16-bit timer, read
the high-order byte first. When writing to a 16-bit timer, write the
low-order byte first. The 16-bit timer cannot perform the correct op-
eration when reading during the write operation, or when writing
during the read operation.
Fig. 24 Timer block diagram
CNTR0 active
edge switch bit
Timer 1 count source
selection bit
Real time port
control bit “0”
“1”
P55/CNTR1
“0”
XIN/16
(XCIN/16 in
φ = XCIN/2)
CNTR1 active
edge switch bit
“10”
Timer Y stop
control bit
Falling edge detection
Timer Y
interrupt
Pulse width HL continuously measurement mode
Rising edge detection
“00”,“01”,“11”
Timer Y operating
mode bit
Timer X
interrupt
Timer X mode register
write signal
P54/CNTR0
Q
T
S
P54 direction register
Pulse output mode
P54 latch
Timer X stop
control bit
“0”
“1”
Timer X write
control bit
Q D
Latch
Q D
Latch
“1”
“0”
“1”
“10”
Timer X operat-
ing mode bits
“00”,“01”,“11”
XIN/16
(XCIN/16 in
φ = XCIN/2)
Pulse width
measurement
mode
CNTR0 active
edge switch bit
Pulse output mode
Q
T
S
“0”
P50 direction register
P50 latch
“1”
TOUT output
active edge
switch bit “0”
Timer 2 write
control bit
“0”
“1”
TOUT output
control bit
“1”
P50/TOUT
XCIN
Timer 3 count
source selection bit
“0”
“1”
Timer
2interrupt
Timer
3interrupt
TOUT output control bit
Timer 2 count source
selection bit
Timer
1interrupt
Data bus
XIN/16
(XCIN/16 in
φ = XCIN/2)
XIN/16
(XCIN/16 in
φ = XCIN/2)
XIN/16(XCIN/16 in
φ = XCIN/2)
P56 direction register “0”
Real time port
control bit “1”
P56/RTP0
P56 latch
P57 direction register “0”
Real time port
control bit “1”
P57/RTP1
P57 latch
P56 data for real time port
P57 data for real time port
Timer Y (low) (8)
Timer Y (high) (8)
Timer 3 latch (8)
Timer 3 (8)
Timer 1 latch (8)
Timer 1 (8)
Timer 2 latch (8)
Timer 2 (8)
Timer X (low) (8)
Timer X (high) (8)
Timer X (low) latch (8)
Timer X (high) latch (8)
Timer Y (low) latch (8)
Timer Y (high) latch (8)
Period
measurement mode