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2.2.8 Operation of timer A (two-phase pulse signal process in event counter mode,
multiply-by-4 mode selected)
In processing two-phase pulse signals in event counter mode, choose functions from those listed in Table
2.2.7. Operations of the circled items are described below. Figure 2.2.18 shows the operation timing, and
Figure 2.2.19 shows the set-up procedure.
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Operation
Note
Count start flag
Timer Ai interrupt
request bit
Note: First set to "Reload type" operation. Once the first counting pulse has occurred, the timer may be changed to "Free-Run type".
Figure 2.2.18. Operation timing of two-phase pulse signal process in event counter mode, multiply-by-4 mode selected
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
Table 2.2.7. Choosed functions
Item
Count operation type
Reload type
O
Free run type
Note: Timer A3 alone can be selected. Timer A2 is solely used for normal processes, and timer A4 is solely used for 4-
multiplication processes.
(1) Setting the count start flag to "1" causes the counter to count effective edges of the count source.
(2) Even if an underflow occurs, the content of the reload register is not reloaded, but the count
continues. At this time, the interrupt request bit goes to "1".
(3) Even if an overflow occurs, the content of the reload register is not reloaded, but the count
continues. At this time, the interrupt request bit goes to "1".
• The up count or down count conditions are as follows:
Table 2.2.8. The up count or down count conditions
Input signal to the
TAi
pin
OUT
"H" level
Up count
"L" level
Rising
Falling
• Set TAi
pin and TAi
IN
OUT
(1) Start count
"H"
TAi
OUT
"L"
"H"
TAi
IN
"L"
FFFF
16
(Note)
0000
16
Set to "1" by software
"1"
"0"
"1"
"0"
page 24 of 354
Set-up
Processing two- phase
pulses (Note)
Input signal to the
TAi
pin
IN
Rising
Down
count
Falling
"L" level
"H" level
pin's port direction register to "0".
(2) Underflow
Cleared to "0" when interrupt request is accepted, or cleared by software
Item
Set-up
Normal processing
O
4-multiplication processing
Input signal to the
Input signal to the
TAi
pin
OUT
"H" level
"L" level
Rising
Falling
(3) Overflow
2. Timer A
TAi
pin
IN
Falling
Rising
"H" level
"L" level
Time
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