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Timer A
Mitsubishi microcomputers
M30201 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
196
In one-shot timer mode, choose functions from those listed in Table 2.2.10. Operations of the circled
items are described below. Figure 2.2.22 shows the operation timing, and Figure 2.2.23 shows the set-up
procedure.
2.2.10 Operation of Timer A (one-shot timer mode, external trigger selected)
Figure 2.2.22. Operation timing of one-shot mode, external trigger selected
Operation (1) If the TA0IN pin input level changes from “L” to “H” with the count start flag set to “1”, the
counter performs a down count on the count source. At this time, the TA0OUT pin output level
goes to “H” level.
(2) If the value of the counter becomes “000016”, the TA0OUT pin outputs an “L” level, and the
counter reloads the content of the reload register and stops counting. At this time, the timer
A0 interrupt request bit goes to “1”.
(3) If a trigger occurs while a count is in progress, the counter reloads the value of the reload
register again and continues counting. The reload timing is in step with the next count source
input after the trigger.
(4) Setting the count start flag to “0” causes the counter to stop and to reload the content of the
reload register. Also, the TA0OUT pin outputs an “L” level. At this time, the timer A0 interrupt
request bit goes to “1”.
Item
Count source
Pulse output function
Count start condition
Set-up
O
Internal count source (f1 / f8 / f32 / fc32)
No pulses output
Pulses output
External trigger input (falling edge of input signal to the TA0IN pin)
External trigger input (rising edge of input signal to the TA0IN pin)
Timer overflow (TB1/TX0/TX2 overflow)
Writing “1” to the one-shot start flag
Table 2.2.10. Choosed functions
FFFF16
n
000116
Timer A0 interrupt
request bit
Counter
content
(hex)
n = reload register content
Reload
(4) Stop count
One-shot pulse output
from TA0OUT pin
“H”
1 / fi X (n)
“L”
1 / fi X (n+1)
TA0IN pin
input signal
“H”
“L”
“1”
Cleared to “0” when interrupt request is accepted, or cleared by software
“0”
Count start flag
“1”
“0”
(2) Stop count
(1) Start count
(3) Start count
Time
Reload
Start count
Set to “1” by software
Trigger during count
Cleared to “0” by software