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12.5
Operation
12.5.1
Basic Functions
Each channel has TCNT and TGR. TCNT performs up-counting, and is also capable of free-
running operation, periodic counting, and external event counting. Each TGR can be used as an
input capture register or output compare register.
Counter Operation:
When one of bits CST0 to CST2 in TSTR is set to 1, TCNT for the corresponding channel starts
counting. TCNT can operate as a free-running counter, periodic counter, and so on.
• Example of Count Operation Setting Procedure
Figure 12.6 shows an example of the count operation setting procedure.
Operation selection
Select counter clock
Periodic counter
Select counter clearing source
Select output compare register
Set period
Start count operation
<Periodic counter>
Figure 12.6 Example of Counter Operation Setting Procedure
[1]
Free-running counter
[2]
[3]
[4]
[5]
Start count operation
<Free-running counter>
[1]
Select the counter
clock with bits
TPSC2 to TPSC0 in
TCR. At the same
time, select the
input clock edge
with bits CKEG1
and CKEG0 in TCR.
[2]
For periodic counter
operation, select the
TGR to be used as
the TCNT clearing
source with bits
CCLR2 to CCLR0 in
TCR.
[3]
Designate the TGR
selected in [2] as an
output compare
register by means of
TIOR.
[4]
Set the periodic
counter cycle in the
TGR selected in [2].
[5]
Set the CST bit in
TSTR to 1 to start
the counter
operation.
Rev. 1.00, 09/03, page 327 of 704
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