SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
3825 Group
24
TIMERS
The 3825 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”,
an underflow occurs at the next count pulse and the correspond-
ing timer latch is reloaded into the timer and the count is contin-
ued. When a timer underflows, the interrupt request bit corre-
sponding 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. 19 Timer block diagram
CNTR0 active
edge switch bit
Timer 1 count source
selection bit
Real time port
control bit “0”
“1”
P55/CNTR1
“0”
f(XIN)/16
(f(XCIN)/16 in low-speed mode])
CNTR1 active
edge switch bit
“10”
Timer Y stop
control bit
Falling edge detection
Period
measurement mode
Timer Y
interrupt
request
Pulse width HL continuously measurement mode
Rising edge detection
“00”,“01”,“11”
Timer Y operating
mode bits
Timer X
interrupt
request
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”
f(XIN)/16
(f(XCIN)/16 in low-speed mode)
Pulse width
measurement
mode
CNTR0 active
edge switch bit
Pulse output mode
Q
T
S
“0”
P56 direction register
P56 latch
“1”
TOUT output
active edge
switch bit “0”
Timer 2 write
control bit
“0”
“1”
TOUT output
control bit
“1”
P56/TOUT
XCIN
Timer 3 count
source selection bit
“0”
“1”
Timer 2
interrupt
request
Timer 3
interrupt
request
TOUT output control bit
Timer 2 count source
selection bit
Timer 1
interrupt
request
Data bus
f(XIN)/16
(f(XCIN)/16 in low-speed mode])
f(XIN)/16
(f(XCIN)/16 in low-speed mode])
f(XIN)/16(f(XCIN)/16 in low-speed mode])
Internal clock
φ = XCIN/2.
CNTR0
interrupt
request
CNTR1
interrupt
request
Timer Y operating mode bits
“00”,“01”,“10”
“11”
P52 direction register “0”
Real time port
control bit “1”
P52
P52 latch
P53 direction register “0”
Real time port
control bit “1”
P53
P53 latch
P52 data for real time port
P53 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)