Bits 2 to 0—Clock Select 2 to 0 (CKS2/1/0): These bits select one of eight internal clock
sources, obtained by prescaling the system clock (ø), for input to TCNT.
Bit 2
Bit 1
Bit 0
CKS2
CKS1
CKS0
Description
0
0
0
ø/2
(Initial value)
1
ø/32
1
0
ø/64
1
ø/128
1
0
0
ø/256
1
ø/512
1
0
ø/2048
1
ø/4096
12.2.3 Reset Control/Status Register (RSTCSR)
RSTCSR is an 8-bit readable and writable
*1
register that indicates when a reset signal has been
generated by watchdog timer overflow, and controls external output of the reset signal.
Bits 7 and 6 are initialized by input of a reset signal at the
RES
pin. They are not initialized by
reset signals generated by watchdog timer overflow.
Notes: 1. RSTCSR differs from other registers in being more difficult to write. For details see
section 12.2.4, Notes on Register Access.
2. Only 0 can be written in bit 7, to clear the flag.
Bit
Initial value
Read/Write
7
WRST
0
R/(W)
6
RSTOE
0
R/W
5
—
1
—
4
—
1
—
3
—
1
—
0
—
1
—
2
—
1
—
1
—
1
—
*
Watchdog timer reset
Indicates that a reset signal has been generated
Reserved bits
Reset output enable
Enables or disables external output of the reset signal
2
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