r5f21346mnfp Renesas Electronics Corporation., r5f21346mnfp Datasheet - Page 219

• Manufacturer Part Number: r5f21346mnfp
• Description: Single-chip Mcus Incorporates The R8c Cpu Core
• Manufacturer: Renesas Electronics Corporation.

R8C/34M Group
R01UH0131EJ0100 Rev.1.00
Jun 21, 2011
14.3.2
Table 14.2
Notes:
Count source
Count operation
Period
Watchdog timer
initialization conditions
Count start conditions
Count stop condition
Operations at underflow
1. The watchdog timer is initialized when 00h and then FFh is written to the WDTR register. The
2. The WDTON bit cannot be changed by a program. To set this bit, write 0 to bit 0 of address 0FFFFh
3. Write the WDTR register during the count operation of the watchdog timer.
The count source for the watchdog timer is the CPU clock when count source protection mode is disabled.
Table 14.2 lists the Watchdog Timer Specifications (Count Source Protection Mode Disabled).
prescaler is initialized after a reset. This may cause some errors due to the prescaler during the
watchdog timer period.
with a flash programmer.
Count Source Protection Mode Disabled
Item
Watchdog Timer Specifications (Count Source Protection Mode Disabled)
CPU clock
Decrement
Division ratio of prescaler (n) × count value of watchdog timer (m)
n: 16 or 128 (selected by the WDTC7 bit in the WDTC register), or
m: Value set by bits WDTUFS0 and WDTUFS1 in the OFS2 register
Example:
The period is approximately 13.1 ms when:
- The CPU clock frequency is set to 20 MHz.
- The prescaler is divided by 16.
- Bits WDTUFS1 to WDTUFS0 are set to 11b (3FFFh).
• Reset
• Write 00h and then FFh to the WDTR register.
• Underflow
The operation of the watchdog timer after a reset is selected by
the WDTON bit
• When the WDTON bit is set to 1 (watchdog timer is stopped after reset).
• When the WDTON bit is set to 0 (watchdog timer starts automatically after
Stop mode, wait mode (Count resumes from the retained value after exiting.)
• When the PM12 bit in the PM1 register is set to 0.
• When the PM12 bit in the PM1 register is set to 1.
The watchdog timer and prescaler are stopped after a reset and
start counting when the WDTS register is written to.
reset).
The watchdog timer and prescaler start counting automatically after a reset.
Watchdog timer interrupt
Watchdog timer reset (refer to 5.5 Watchdog Timer Reset )
2 when selecting the low-speed clock (CM07 bit in CM0 register = 1)
(2)
in the OFS register (address 0FFFFh).
CPU clock
Specification
(3)
14. Watchdog Timer
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