3820 GROUP USER’S MANUAL
1-24
MITSUBISHI MICROCOMPUTERS
3820 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Timer Y
Timer Y is a 16-bit timer that can be selected in one of four modes.
Timer mode
The timer counts f(X
IN
)/16 (or f(X
CIN
)/16 in low-speed mode).
Period measurement mode
CNTR
1
interrupt request is generated at rising/falling edge of
CNTR
1
pin input signal. Simultaneously, the value in timer Y latch
is reloaded in timer Y and timer Y continues counting down/Except
for the above-mentioned, the operation in period measurement
mode is the same as in timer mode.
The timer value just before the reloading at rising/falling of CNTR
1
pin input signal is retained until the timer Y is read once after the
reload.
The rising/falling timing of CNTR
1
pin input signal is found by
CNTR
1
interrupt. When using a timer in this mode, set the corre-
sponding port P5
5
direction register to input mode.
Event counter mode
The timer counts signals input through the CNTR
1
pin.
Except for this, the operation in event counter mode is the same
as in timer mode. When using a timer in this mode, set the corre-
sponding port P5
5
direction register to input mode.
Pulse width HL continuously measurement mode
CNTR
1
interrupt request is generated at both rising and falling
edges of CNTR
1
pin input signal. Except for this, the operation in
pulse width HL continuously measurement mode is the same as in
period measurement mode. When using a timer in this mode, set
the corresponding port P5
5
direction register to input mode.
Note on CNTR
1
Interrupt Active Edge Selec-
tion
CNTR
1
interrupt active edge depends on the CNTR
1
active edge
switch bit. However, in pulse width HL continuously measurement
mode, CNTR
1
interrupt request is generated at both rising and
falling edges of CNTR
1
pin input signal regardless of the setting of
CNTR
1
active edge switch bit.
Fig. 20 Structure of timer Y mode register
Timer Y mode register
(TYM : address 0028
16
)
Not used (return "0" when read)
Timer Y operating mode bits
b5 b4
0 0 : Timer mode
0 1 : Period measurement mode
1 0 : Event counter mode
1 1 : Pulse width HL continuously
measurement mode
CNTR
1
active edge switch bit
CNTR
1
interrupt
0 : Falling edge active
1 : Rising edge active
Period measurement mode
0 : Measure falling edge to falling edge
1 : Measure rising edge to rising edge
Event counter mode
0 : Rising edge active
1 : Falling edge active
Timer Y stop control bit
0 : Count start
1 : Count stop
7
0