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Bit
Bit Name
2
CKS2
1
CKS1
0
CKS0
Notes: 1. Only 0 can be written, to clear the flag.
2. When OVF is polled with the interval timer interrupt disabled, OVF = 1 must be read at
least twice.
• TCSR_1
Bit
Bit Name
7
OVF
6
WT/IT
5
TME
Initial
Value
R/W
0
R/W
0
R/W
0
R/W
Initial
Value
R/W
1
0
R/(W)*
0
R/W
0
R/W
Description
Clock Select 2 to 0
Selects the clock source to be input to. The overflow
frequency for φ = 10 MHz is enclosed in parentheses.
000: φ/2 (frequency: 51.2 µs)
001: φ/64 (frequency: 1.64 ms)
010: φ/128 (frequency: 3.28 ms)
011: φ/512 (frequency: 13.1 ms)
100: φ/2048 (frequency: 52.4 ms)
101: φ/8192 (frequency: 209.7 ms)
110: φ/32768 (frequency: 0.84 s)
111: φ/131072 (frequency: 3.36 s)
Description
Overflow Flag
Indicates that TCNT has overflowed (changes from H'FF
to H'00).
[Setting condition]
When TCNT overflows (changes from H'FF to H'00)
However, when internal reset request generation is
selected in watchdog timer mode, OVF is cleared
automatically by the internal reset.
[Clearing conditions]
When TCSR is read when OVF = 1*
OVF
When 0 is written to TME
Timer Mode Select
Selects whether the WDT is used as a watchdog timer
or interval timer.
0: Interval timer mode
1: Watchdog timer mode
Timer Enable
When this bit is set to 1, TCNT starts counting.
When this bit is cleared, TCNT stops counting and is
initialized to H'00.
2
, then 0 is written to
Rev. 1.00, 05/04, page 225 of 544
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