Datasheet

Section 13 Watchdog Timer
Rev.6.00 Sep. 27, 2007 Page 586 of 1268
REJ09B0220-0600
Bit 6
WT/IT Description
0 Interval timer: Sends the CPU an interval timer interrupt request (WOVI)
when TCNT overflows (Initial value)
1 Watchdog timer: Generates the WDTOVF signal
*
1
when TCNT overflows
*
2
Notes: 1. The WDTOVF pin function cannot be used in the F-ZTAT versions.
2. For details of the case where TCNT overflows in watchdog timer mode, see section
13.2.3, Reset Control/Status Register (RSTCSR).
Bit 5—Timer Enable (TME): Selects whether TCNT runs or is halted.
Bit 5
TME Description
0 TCNT is initialized to H'00 and halted (Initial value)
1 TCNT counts
Bits 4 and 3—Reserved: These bits cannot be modified and are always read as 1.
Bits 2 to 0—Clock Select 2 to 0 (CKS2 to CKS0): These bits select one of eight internal clock
sources, obtained by dividing the system clock (φ), for input to TCNT.
Description
Bit 2
CKS2
Bit 1
CKS1
Bit 0
CKS0 Clock Overflow Period (when φ = 20 MHz)
*
0 0 0 φ/2 (Initial value) 25.6 µs
1 φ/64 819.2 µs
1 0 φ/128 1.6 ms
1 φ/512 6.6 ms
1 0 0 φ/2048 26.2 ms
1 φ/8192 104.9 ms
1 0 φ/32768 419.4 ms
1 φ/131072 1.68 s
Note: * The overflow period is the time from when TCNT starts counting up from H'00 until overflow
occurs.