Z8F1680SH020SG Datasheet, PDF (167/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
142
11.1.2.3. WDT Reset in Normal Operation
The WDT forces the device into the Reset state if it is configured to generate a Reset when
a time-out occurs; the WDT status bit is set to 1 (for details, see the Reset Status Register
section on page 40). For more information about Reset and the WDT status bit, see the
Reset, Stop Mode Recovery and Low-Voltage Detection section on page 31. Following a
Reset sequence, the WDT Counter is initialized with its reset value.
11.1.2.4. WDT Reset in STOP Mode
If enabled in STOP Mode and configured to generate a Reset when a time-out occurs and
the device is in STOP Mode, the WDT initiates a Stop Mode Recovery. Both the WDT
status bit and the stop bit in the Reset Status Register (RSTSTAT) are set to 1 following a
WDT time-out in STOP Mode. For more information, see the Reset, Stop Mode Recovery
and Low-Voltage Detection section on page 31.
11.1.3. Watchdog Timer Reload Unlock Sequence
Writing the unlock sequence to the Watchdog Timer Reload High (WDTH) Register
address unlocks the two Watchdog Timer Reload registers (WDTH and WDTL) to allow
changes to the time-out period. These write operations to the WDTH Register address
produce no effect on the bits in the WDTH Register. The locking mechanism prevents
unwarranted writes to the Reload registers. The following sequence is required to unlock
the Watchdog Timer Reload registers (WDTH and WDTL) for write access.
1. Write 55H to the Watchdog Timer Reload High Register (WDTH).
2. Write AAH to the Watchdog Timer Reload High Register (WDTH).
3. Write the appropriate value to the Watchdog Timer Reload High Register (WDTH).
4. Write the appropriate value to the Watchdog Timer Reload Low Register (WDTL).
After this write occurs, the Watchdog Timer Reload registers are again locked.
All steps of the WDT Reload Unlock sequence must be written in the sequence defined
above. The values in these WDT Reload registers are loaded into the counter every time a
WDT instruction is executed.
11.2. Watchdog Timer Register Definitions
The two Watchdog Timer Reload registers (WDTH and WDTL) are described in the
following tables.
PS025015-1212
PRELIMINARY
Watchdog Timer