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
CKS2
CKS1
0
0
1
1
0
1
10.2.3 Reset Control/Status Register (RSTCSR)
RSTCSR is an 8-bit readable and writable*
generated by watchdog timer overflow, and controls external output of the reset signal.
Bit
WRST
Initial value
Read/Write
R/(W)
Watchdog timer reset
Indicates that a reset signal has been generated
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 is write-protected by a password. For details see section 10.2.4, Notes on
Register Access.
2. Only 0 can be written in bit 7 to clear the flag.
3. With the masked ROM version, enable and disable can be set. With the F-ZTAT
version, do not set enable.
Bit 0
CKS0
Description
0
ø/2
1
ø/32
0
ø/64
1
ø/128
0
ø/256
1
ø/512
0
ø/2048
1
ø/4096
7
6
RSTOE
—
0
0
2
*
R/W
—
Reset output enable
Enables or disables external output of the reset signal
1
register that indicates when a reset signal has been
5
4
—
—
1
1
—
—
Reserved bits
*3
3
2
—
—
1
1
—
—
(Initial value)
1
0
—
1
1
—
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