Chapter 9 Watchdog Timer; Functions Of Watchdog Timer - NEC mPD780024AS Series Preliminary User's Manual

9.1 Functions of Watchdog Timer

The watchdog timer has the following functions.
• Watchdog timer
• Interval timer
• Oscillation stabilization time selection
Caution Select the watchdog timer mode or the interval timer mode with the watchdog timer mode
register (WDTM) (The watchdog timer and the interval timer cannot be used simultaneously).
Figure 9-1 shows a block diagram of the watchdog timer.
f
X
8
f /2
X
Oscillation stabilization
time select register
(OSTS)

CHAPTER 9 WATCHDOG TIMER

Figure 9-1. Block Diagram of Watchdog Timer
Clock
Divider
input
controller
RUN Division mode
selection circuit
OSTS2 OSTS1 OSTS0 WDCS2 WDCS1 WDCS0
Watchdog timer
clock select
register (WDCS)
Internal bus
Preliminary User's Manual U16035EJ1V0UM
Divided
clock
Output
selection
controller
circuit
3
WDTM3
RUN WDTM4
Watchdog timer
mode register
(WDTM)
INTWDT
RESET
WDT mode signal
157