Figure 9-17 shows an example of watchdog timer operations.
Example: ø = 2 MHz and the desired overflow period is 30 ms.
2 × 106
8192
× 30 × 10–3 = 7.3
The value set in TCW should therefore be 256 – 8 = 248 (H'F8).
TCW overflow
H'FF
H'F8
TCW count
value
H'00
Start
H'F8 written
in TCW
Reset
H'F8 written in TCW
Internal reset
signal
512 øOSC clock cycles
Figure 9-17 Typical Watchdog Timer Operations (Example)
Watchdog Timer Operation States
9.6.4
Table 9-18 summarizes the watchdog timer operation states.
Table 9-18 Watchdog Timer Operation States
Operation
Module
Subactive Subsleep Standby Standby
Mode
Reset
Active
Sleep
Watch
TCW
Reset
Functions Functions Halted
Functions/ Halted
Halted
Halted
Halted*
TCSRW
Note:
Reset
Functions Functions Retained Functions/ Retained Retained Retained
Halted*
*
Functions when øw/32 is selected as the input clock.
239
ETC [ ETC ]
