24
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
3827 Group
MITSUBISHI MICROCOMPUTERS
Timer 1, Timer 2, Timer 3
Timer 1, timer 2, and timer 3 are 8-bit timers. The count source for
each timer can be selected by timer 123 mode register. The timer
latch value is not affected by a change of the count source. How-
ever, because changing the count source may cause an
inadvertent count down of the timer. Therefore, rewrite the value of
timer whenever the count source is changed.
G
Timer 2 write control
If the timer 2 write control bit is “0”, when the value is written in the
at the same time.
If the timer 2 write control bit is “1”, when the value is written in the
address of timer 2, the value is loaded only in the latch. The value
in the latch is loaded in timer 2 after timer 2 underflows.
G
Timer 2 output control
When the timer 2 (T
OUT
) is output enabled, an inversion signal
from the T
OUT
pin is output each time timer 2 underflows.
In this case, set the port shared with the T
OUT
pin to the output.
I
Notes on timer 1 to timer 3
When the count source of timer 1 to 3 is changed, the timer count-
ing value may be changed large because a thin pulse is generated
in count input of timer . If timer 1 output is selected as the count
source of timer 2 or timer 3, when timer 1 is written, the counting
value of timer 2 or timer 3 may be changed large because a thin
pulse is generated in timer 1 output.
Therefore, set the value of timer in the order of timer 1, timer 2 and
timer 3 after the count source selection of timer 1 to 3.
Fig. 20 Structure of timer 123 mode register
T
OUT
output active edge switch bit
0 : Start at “H” output
1 : Start at “L” output
T
OUT
/
φ
output control bit
0 : T
OUT
/
φ
output disabled
1 : T
OUT
/
φ
output enabled
Timer 2 write control bit
0 : Write data in latch and counter
1 : Write data in latch only
Timer 2 count source selection bit
0 : Timer 1 output
1 : f(X
IN
)/16
(or f(X
CIN
)/16 in low-speed mode)
Timer 3 count source selection bit
0 : Timer 1 output
1 : f(X
IN
)/16
(or f(X
CIN
)/16 in low-speed mode)
Timer 1 count source selection bit
0 : f(X
IN
)/16
(or f(X
CIN
)/16 in low-speed mode)
1 : f(X
CIN
)
Not used (return “0” when read)
Timer 123 mode register
(T123M :address 0029
16
)
Note :
Internal clock
φ
is X
CIN
/2 in the low-speed mode.
b7
b0