Datasheet

Section 13 Timer Z
Rev.5.00 Nov. 02, 2005 Page 199 of 500
REJ09B0027-0500
13.4 Operation
13.4.1 Counter Operation
When one of bits STR0 and STR1 in TSTR is set to 1, the TCNT counter for the corresponding
channel begins counting. TCNT can operate as a free-running counter, periodic counter, for
example. Figure 13.7 shows an example of the counter operation setting procedure.
[1] Select the counter
clock with bits
TPSC2 to TPSC0 in
TCR. When an external
clock is selected, select
the external clock edge
with bits CKEG1
and CKEG0 in TCR.
[2] For periodic counter
operation, select the
TCNT clearing
source with bits
CCLR2 to CCLR0 in
TCR.
[3] Designate the general
register selected in [2]
as an output compare
register by means of
TIOR.
[4] Set the periodic counter
cycle in the general
register selected
in [2].
[5] Set the STR bit in TSTR
to 1 to start the counter
operation.
Operation selection
Periodic counter
Free-running counter
[1]
Select counter clock
[2]
Select counter clearing source
[3]
Select output compare register
[5]
Start count operation
[4]Set period
Figure 13.7 Example of Counter Operation Setting Procedure
1. Free-running count operation and periodic count operation
Immediately after a reset, the TCNT counters for channels 0 and 1 are all designated as free-
running counters. When the relevant bit in TSTR is set to 1, the corresponding TCNT counter
starts an increment operation as a free-running counter. When TCNT overflows, the OVF flag
in TSR is set to 1. If the value of the OVIE bit in the corresponding TIER is 1 at this point,
timer Z requests an interrupt. After overflow, TCNT starts an increment operation again from
H'0000.