Renesas M16C FAMILY, User Manual

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Rev.2.00 Oct 16, 2006 page 22 of 354
REJ09B0340-0200
M30245 Group 2. Timer A
Figure 2.2.16. Operation timing of two-phase pulse signal process in event counter mode, normal mode selected
2.2.7 Operation of timer A (two-phase pulse signal process in event counter mode,
normal mode selected)
In processing two-phase pulse signals in event counter mode, choose functions from those listed in Table
2.2.6. Operations of the circled items are described below. Figure 2.2.16 shows the operation timing, and
Figure 2.2.17 shows the set-up procedure.
Item
Count operation type
Two-phase pulses
process (Note)
Set-up
O
O
Reload type
Free run type
Normal processing
4-multiplication processing
Table 2.2.6. Choosed functions
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 timer Ai 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 timer Ai interrupt request bit goes to “1”.
• The up count or down count conditions are as follows:
If a rising edge is present at the TAi
IN
pin when the input signal level to the TAi
OUT
pin is “H”,
an up count is performed.
If a falling edge is present at the TAi
IN
pin when the input signal level to the TAi
OUT
pin is “H”,
a down count is performed.
• Set TAi
IN
pin and TAi
OUT
pin's port direction register to “0”.
Operation
Note
0000
16
Count start flag
Timer Ai interrupt
request bit
“1”
“0”
“1”
“0”
FFFF
16
Counter content (hex)
Input pulse
TAi
OUT
“H”
“L”
“H”
“L”
TAi
IN
Set to “1” by software
Cleared to “0” when interrupt request is accepted, or cleared by software
(1) Start count
(2) Underflow (3)
Overflow
Time
Note 1: First set to “Reload type” operation. Once the first counting pulse has occurred, the timer may be changed to “Free-Run type”.
(Note)