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2.2.5 Operation of Timer A (event counter mode, reload type selected)
In event counter mode, choose functions from those listed in Table 2.2.4. Operations of the circled items
are described below. Figure 2.2.12 shows the operation timing, and Figure 2.2.13 shows the set-up
procedure.
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Operation
Count start flag
Up/down flag
Timer Ai interrupt
request bit
Figure 2.2.12. Operation timing of event counter mode, reload type selected
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
Table 2.2.4. Choosed functions
Item
Count source
Input signal to TAi
O
(counting falling edges)
Input signal to TAi
(counting rising edges)
TAj overflow
Note: j = i – 1, but j = 4 when i = 0.
(1) Setting the count start flag to "1" causes the counter to count the falling edges of the count
source.
(2) If an underflow occurs, the content of the reload register is reloaded, and the count continues.
At this time, the timer Ai interrupt request bit goes to "1".
(3) If switching from an up count to a down count or vice versa while a count is in progress, the
switch takes effect from the next effective edge of the count source.
(4) Setting the count start flag to "0" causes the counter to hold its value and to stop.
(5) If an overflow occurs, the content of the reload register is reloaded, and the count continues.
At this time, the timer Ai interrupt request bit goes to "1".
n = reload register content
FFFF
16
(1) Start count
n
0000
16
Set to "1" by software
"1"
"0"
"1"
"0"
"1"
"0"
page 18 of 354
Set-up
Item
Pulse output function
IN
Count operation type
IN
Factor for switching
between up and
down
(3) Switch count
(2) Underflow
Cleared to "0" by
software
Set to "1" by software
Cleared to "0" when interrupt request is accepted, or cleared by software
Set-up
O
No pulses output
Pulses output
O
Reload type
Free-run type
O
Content of up/down flag
Input signal to TAi
OUT
(5) Overflow
(4) Stop count
Start count again
Time
Set to "1" by software
2. Timer A
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