Timer A
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
2-26
2.2.9 Operation of Timer A (one-shot timer mode)
Figure 2.2.20. Operation timing of one-shot mode
In one-shot timer mode, choose functions from those listed in Table 2.2.9. Operations of the circled items
are described below. Figure 2.2.20 shows the operation timing, and Figure 2.2.21 shows the set-up
procedure.
Operation
Note
Note: j = i – 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4.
(1) Setting the one-shot start flag to “1” with the count start flag set to “1” causes the counter to
perform a down count on the count source. At this time, the TAiOUT pin outputs an “H” level.
(2) The instant the value of the counter becomes “000016”, the TAiOUT pin outputs an “L” level,
and the counter reloads the content of the reload register and stops counting. At this time, the
timer Ai interrupt request bit goes to “1”.
(3) If a trigger occurs while a count is in progress, the counter reloads the value in 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 TAiOUT pin outputs an “L” level. At this time, the timer Ai interrupt
request bit goes to “1”.
When the timer Ai register is set to “000016”, the counter does not operate and the timer Ai
interrupt request is not generated. When the pulse is set to output, the pulse does not output
from the TAiOUT pin.
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 TAiIN pin)
External trigger input (rising edge of input signal to the TAiIN pin)
Timer overflow (TB2/TAj/TAk overflow)
Writing “1” to the one-shot start flag
Table 2.2.9. Choosed functions
FFFF16
n
000116
Timer Ai interrupt
request bit
Counter
content
(hex)
n = reload register content
Reload
One-shot pulse output
from TAiOUT pin
“H”
1 / fi X (n)
“L”
Time
Reload
1 / fi X (n+1)
Write signal to
one-shot start flag
“1”
“0”
Count start flag
“1”
“0”
(1) Start count
Cleared to “0” when interrupt request is accepted, or cleared by software
(2) Stop count
(3) Start count
(4) Stop count
Start count
Reload
Set to “1” by software
Cleared to “0” by software