WATCHDOG TIMER V1.1
Chapter 2 Watchdog Timer
MCU-AN-500013-E-11 – Page 7
2.4 NVR (Non-Volatile Register) function
The NVR interface enables users to select hardware or software watchdog timer by
modifying the 16-bit watchdog timer selection ID. Please note that the watchdog timer
selection ID cannot be modified while the CPU is running, therefore please modify NVR in
Flash Area first, then the MCU will copy these values to NVR interface (IO Area)
automatically after a reset.
Figure 2-4 shows the basic configuration of serial programming connection for flash memory
products.
Figure 2-4: Retrieval of NVR during Reset
Please note that either the SWWDT or HWWDT can work in the same time. NVR is used to
decide which one is working.
These 16 bits of WDTH and WDTL are loaded from the flash address FFBE
H
, FFBF
H
after a
reset. The initial values are determined by the pre-loaded values in the NVR flash area.
Write certain values to the address FFBE
H
and FFBF
H
to select watchdog timer’s mode.
Table 2-1 shows watchdog timer selection ID.
WDTH[7:0], WDTL[7:0]
Function
A596
H
The HWWDT is disabled and the SWWDT is enabled.
A597
H
The HWWDT is selected and the SWWDT is disabled. [It
can be stopped in one of the standby modes
(stop/sleep/timebase timer/watch mode).]
Other than the above values
The WHWDT is selected and the SWWDT is disabled. [It
keeps running in one of the standby modes
(stop/sleep/timebase timer/watch mode).]
Table 2-1: Watchdog Timer Selection ID
