SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
38C1 Group
23
Timer Y
Timer Y is a 16-bit timer that can be selected in one of four modes.
(1) Timer mode
The timer counts the followings;
f(X
IN
)/16 in middle-, or high-speed mode
f(X
CIN
)/16 in low-speed mode
f(XR
OSC
) divided by 16 in ring oscillator mode
(2) 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. Ex-
cept for the above-mentioned, the operation in period measure-
ment 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
3
direction register to input mode.
(3) 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
3
direction register to input mode.
(4) Pulse width HL continuously measure-
ment 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
3
direction register to input mode.
I
Note on CNTR
1
interrupt active edge selection
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
, initial value: 00
16
)
b
7
b
0
Not used (returns
“
0
”
when read)
(Do not write
“
1
”
to these bits.)
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
0 : Count at rising edge in event counter mode
Measure the falling edge to falling edge
period in period measurement mode
Falling edge active for CNTR
1
interrupt
1 : Count at falling edge in event counter mode
Measure the rising edge period in period
measurement mode
Rising edge active for CNTR
1
interrupt
Timer Y stop control bit
0 : Count start
1 : Count stop