Z8F64220100ZDA Zilog, Z8F64220100ZDA Datasheet - Page 109
Manufacturer Part Number
ADAPTER ICE Z8 ENCORE 64K 64LQFP
Specifications of Z8F64220100ZDA
For Use With/related Products
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Watchdog Timer Reload Unlock Sequence
STOP mode. For more information on Stop Mode Recovery, see
If interrupts are enabled, following completion of the Stop Mode Recovery the eZ8 CPU
responds to the interrupt request by fetching the Watchdog Timer interrupt vector and exe-
cuting code from the vector address.
WDT Reset in Normal Operation
If configured to generate a Reset when a time-out occurs, the Watchdog Timer forces the
device into the Reset state. The WDT status bit in the Watchdog Timer Control register is
set to 1. For more information on Reset, see
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 Watchdog Timer initiates a Stop Mode Recovery. Both
the WDT status bit and the STOP bit in the Watchdog Timer Control register are set to 1
following WDT time-out in STOP mode. Default operation is for the WDT and its RC
oscillator to be enabled during STOP mode.
WDT RC Disable in STOP Mode
To minimize power consumption in STOP Mode, the WDT and its RC oscillator can be
disabled in STOP mode. The following sequence configures the WDT to be disabled when
the Z8 Encore! XP
1. Write 55H to the Watchdog Timer Control register (WDTCTL).
2. Write AAH to the Watchdog Timer Control register (WDTCTL).
3. Write 81H to the Watchdog Timer Control register (WDTCTL) to configure the WDT
This sequence only affects WDT operation in STOP mode.
Writing the unlock sequence to the Watchdog Timer (WDTCTL) Control register address
unlocks the three Watchdog Timer Reload Byte registers (WDTU, WDTH, and WDTL) to
allow changes to the time-out period. These write operations to the WDTCTL register
address produce no effect on the bits in the WDTCTL register. The locking mechanism
prevents spurious writes to the Reload registers. Follow the steps below to unlock the
Watchdog Timer Reload Byte registers (WDTU, WDTH, and WDTL) for write access.
and its oscillator to be disabled during STOP Mode. Alternatively, write 00H to the
Watchdog Timer Control register (WDTCTL) as the third step in this sequence to
reconfigure the WDT and its oscillator to be enabled during STOP mode.
on page 45.
to the Watchdog Timer Control register (WDTCTL).
F64XX Series devices enter STOP Mode following execution of a
Reset and Stop Mode Recovery
Z8 Encore! XP
Reset and Stop Mode
on page 45.