9. Timers
Rev.3.00 Jul. 19, 2007 page 246 of 532
REJ09B0397-0300
Bits 2 to 0—Clock Select 2 to 0 (CKS2 to CKS0):
Bits 2 to 0 select the clock to be input to
TCW.
Bit 2:
CKS2
Bit 1:
CKS1
Bit 0:
CKS0
Description
0 0 0 Internal
clock:
φ
/64
1
Internal
clock:
φ
/128
1 0 Internal
clock:
φ
/256
1
Internal
clock:
φ
/512
1 0 0 Internal
clock:
φ
/1024
1
Internal
clock:
φ
/2048
1 0 Internal
clock:
φ
/4096
1
Internal
clock:
φ
/8192
(initial value)
9.6.3 Operation
The watchdog timer is provided with an 8-bit counter that increments with each input clock pulse.
If 1 is written to WDON while writing 0 to B2WI when TCSRWE in TCSRW is set to 1, TCW
begins counting up. When a clock pulse is input after the TCW count value has reached H'FF, the
watchdog timer overflows and an internal reset signal is generated one base clock (
φ
) cycle later.
The internal reset signal is output for a period of 512
φ
osc
clock cycles. TCW is a writable counter,
and when a value is set in TCW, the count-up starts from that value. An overflow period in the
range of 1 to 256 input clock cycles can therefore be set, according to the TCW value.
Figure 9.9 shows an example of watchdog timer operation.
Содержание F-ZTAT H8 Series
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