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Figure 9-18 shows an example of watchdog timer operations.
H'F8
TCW overflow
Start
H'F8 written
in TCW
H'F8 written in TCW
Reset
Internal reset
signal
512 ø
OSC
clock cycles
H'FF
H'00
TCW count
value
Example: ø = 2 MHz and the desired overflow period is 30 ms.
The value set in TCW should therefore be 256 – 8 = 248 (H'F8).
2
×
10
6
×
30
×
10
–3
= 7.3
8192
Figure 9-18 Typical Watchdog Timer Operations (Example)
9.6.4
Watchdog Timer Operation States
Table 9-18 summarizes the watchdog timer operation states.
Table 9-18 Watchdog Timer Operation States
Operation
Mode
Reset
Active
Sleep
Watch
Subactive Subsleep Standby
Module
Standby
TCW
Reset
Functions
Functions Halted
Functions/
Halted
*
Halted
Halted
Halted
TCSRW
Reset
Functions
Functions Retained
Functions/
Halted
*
Retained
Retained
Retained
Note:
*
Functions when øw/32 is selected as the input clock.
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