202
Timer A
M
i
t
s
u
M
S
b
i
s
3
M
h
0
I
C
i
m
2
R
i
1
O
c
r
8
C
o
c
o
G
M
m
p
r
P
u
t
u
T
e
r
p
R
s
o
U
S
I
N
G
L
E
-
C
H
I
P
1
6
-
B
I
T
C
M
O
O
E
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
Note: j = i – 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4.
(1) If the TAi
IN
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 TAi
OUT
pin output level
goes to “H” level.
(2) If the value of the counter becomes “0000
16
”, the TAi
OUT
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 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 TAi
OUT
pin outputs an “L” level. At this time, the timer Ai interrupt
request bit goes to “1”.
Table 2.2.10. Choosed functions
Item
Count source
Pulse output function
Count start condition
Set-up
O
O
O
Internal count source (f
1
/ f
8
/ f
32
/ fc
32
)
No pulses output
Pulses output
External trigger input (falling edge of input signal to the TAi
IN
pin)
External trigger input (rising edge of input signal to the TAi
IN
pin)
Timer overflow (TB2/TAj/TAk overflow)
Writing “1” to the one-shot start flag
FFFF
16
n
0001
16
Timer Ai interrupt
request bit
C
n = reload register content
Reload
Reload
(4) Stop count
One-shot pulse output
from TAi
OUT
pin
“H”
“L”
1 / fi X (n)
1 / fi X (n+1)
TAi
IN
pin
input signal
“H”
“L”
“1”
“0”
Cleared to “0” when interrupt request is accepted, or cleared by software
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