One-Shot Timer Mode - Renesas M16C Series User Manual

M30240 Group

2.2.2.8 One-shot timer mode

In one-shot timer mode, select functions from those listed in Table 2.9 . An example using the indicated
options is described below. Figure 2.21 shows the operation timing, and Figure 2.22 shows the set-up
procedure.
Table 2.9: Timer A one-shot timer mode
Item
Count source O
Pulse output function
O
Count start condition
O
Note: j = i - 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4
Operation
(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 TAi
(2) The instant the value of the counter becomes "0000
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 TAi
to "1".
FFFF
0001
Count start flag
Write signal to
one-shot start flag
"H"
One-shot pulse output
from TAi pin
OUT
"L"
"1"
Timer Ai interrupt
request bit
"0"
Figure 2.21: Operation timing of one-shot mode
Rev.1.00 Sep 24, 2003 Page 161 of 360
Internal count source (f1/f8/f32)
No pulses output
Pulses output
External trigger input (falling edge of input signal to the TAi
External trigger input (rising edge of input signal to the TAi
Timer overflow (TB2/TAj/TAk overflow)
Writing "1" to the one-shot start flag
pin outputs an "L" level. At this time, the Timer Ai interrupt request bit goes
OUT
n = reload register content
(2) Stop count
16
(1) Start count
n
Reload
16
Set to "1" by software
"1"
"0"
1 / f X (n)
i
Cleared to "0" when interrupt request is accepted, or cleared by software
Set-up
IN
IN
pin outputs an "H" level.
OUT
", the TAi pin outputs an "L" level, and
16 OUT
(3) Start count
Start count
Reload
Cleared to "0" by software
1 / f X (n+1)
i
Timer A
pin)
pin)
(4) Stop count
Reload
Time