W681308
XXXX PRODUCT DESCRIPTION
Control Bit
EWT
Name
Function
Enable Watchdog
timer Reset
Setting this bit will enable the Watchdog timer Reset function.
This bit helps in putting the watchdog timer into a know state. It also helps in
resetting the watchdog timer before a time-out occurs. Failing to set the EWT before
time-out will cause an interrupt, if EWDI (EIE.4) is set, and 512 clocks after that a
watchdog timer reset will be generated if EWT is set. This bit is self-clearing.
Reset Watchdog
Timer
RWT
Table 8 Watchdog Control Bits
WTRF is set to a 1 on a Watchdog timer reset, set to 0 on power on/down resets. WTRF is not altered by an external reset.
POR is set to 1 by a power-on reset. EWT is cleared to 0 on a Power-on reset and unaffected by other resets.
To prevent software from accidentally enabling or disabling the watch dog reset function, the bit of WDCON requires Time
Access (TA) procedure to write.
Example:
mov TA, #0AAH
mov TA, #055H
clr WDIF
WD1, WD0 are Time-out bits for Watchdog Timer located at CKCON.7 and CKCON.6. These bits determine the time-out
period of the watchdog timer. The reset time-out period is 512 clocks longer than the watchdog time-out.
WD1
WD0
Interrupt time-out
Reset time-out
223 + 512
0
0
1
1
0
1
0
1
223
225
226
228
225 + 512
226 + 512
228 + 512
Table 9 Watchdog Timer Timeout Control
27
Rev1.2
NUVOTEM TALEMA [ NUVOTEM TALEMA ]
