HD64F3687GFPV Datasheet, PDF (285/538 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 14 Watchdog Timer
Section 14 Watchdog Timer
The watchdog timer is an 8-bit timer that can generate an internal reset signal for this LSI if a
system crash prevents the CPU from writing to the timer counter, thus allowing it to overflow.
The block diagram of the watchdog timer is shown in figure 14.1.
Internal
oscillator
φ
CLK
PSS
TCSRWD
TCWD
TMWD
[Legend]
TCSRWD: Timer control/status register WD
TCWD: Timer counter WD
PSS:
Prescaler S
TMWD: Timer mode register WD
Internal reset
signal
Figure 14.1 Block Diagram of Watchdog Timer
14.1 Features
• Selectable from nine counter input clocks.
Eight clock sources (φ/64, φ/128, φ/256, φ/512, φ/1024, φ/2048, φ/4096, and φ/8192) or the
internal oscillator can be selected as the timer-counter clock. When the internal oscillator is
selected, it can operate as the watchdog timer in any operating mode.
• Reset signal generated on counter overflow
An overflow period of 1 to 256 times the selected clock can be set.
14.2 Register Descriptions
The watchdog timer has the following registers.
• Timer control/status register WD (TCSRWD)
• Timer counter WD (TCWD)
• Timer mode register WD (TMWD)
WDT0110A_000020020200
Rev.5.00 Nov. 02, 2005 Page 251 of 500
REJ09B0027-0500