Count Source Protection Mode Enabled - Renesas M16C/64C User Manual

M16C/64C Group
15.4.2

Count Source Protection Mode Enabled

fOCO-S is used as the watchdog timer count source when the count source protection mode is
enabled.
Table 15.4 lists the Watchdog Timer Specifications (Count Source Protection Mode Enabled).
Table 15.4 Watchdog Timer Specifications (Count Source Protection Mode Enabled)
Item
Count source
Count operation
Cycle
Watchdog timer
counter refresh
timing
Count start
conditions
Count stop
condition
Operation when
timer underflows
When the CSPRO bit in the CSPR register is 1 (count source protection mode enabled), the watchdog
timer counter underflows every 4096 cycles because the 3 low-order bits are not used.
Also when the CSPRO bit is set to 1 (count source protection mode enabled), the following bits change:
•
The CM14 bit in the CM1 register becomes 0 (125 kHz on-chip oscillator on). It remains
unchanged even if 1 is written, and the 125 kHz on-chip oscillator does not stop.
•
The PM12 bit in the PM1 register becomes 1 (watchdog timer reset when watchdog timer counter
underflows).
•
The CM10 bit in the CM1 register remains unchanged even if 1 is written, and the MCU does not
enter stop mode.
R01UH0092EJ0110 Rev.1.10
Jul 31, 2012
fOCO-S
(The 125 kHz on-chip oscillator clock automatically starts oscillating.)
Decrement
Watchdog timer count value (4096)
-------------------------------------------------------------------------------------------- -
fOCO-S
(The watchdog timer cycle is approximately 32.8 ms.)
•
Reset (refer to 6. "Resets")
•
Write 00h, then FFh to the WDTR register.
•
Underflow
Set the WDTON bit in the OFS1 address to select the watchdog timer operation
after reset.
•
WDTON bit is 1 (watchdog timer is stopped after reset)
The watchdog timer counter and prescaler stop after reset and count starts by
writing to the WDTS register.
•
WDTON bit is 0 (watchdog timer starts automatically after reset)
The watchdog timer counter and prescaler start counting automatically after reset.
None
(The count does not stop in wait mode or by bus hold once started. The MCU does
not enter stop mode.)
Watchdog timer reset (refer to 6.4.8 "Watchdog Timer Reset").
Specification
15. Watchdog Timer
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