Advance Information
UM-TM57PE10_E
8-Bit Microcontroller
20
tenx technology inc.
Preliminary
Rev 1.4, 2012/01/19
3. Peripheral Functional Block
3.1 Watchdog (WDT) / Wakeup (WKT) Timer
The WDT and WKT share the same internal RC Timer. The overflow period of WDT/WKT can be
selected from 14 ms to 138 ms. The WDT/WKT is cleared by the CLRWDT instruction. If the Watchdog
Reset is enabled (WDTE=1), the WDT generates the chip reset signal, otherwise, the WKT only
generates overflow time out interrupt. The WDT/WKT works in both normal mode and sleep mode.
During sleep mode, user can further choose to enable or disable the WDT/WKT by "WKTIE". If
WKTIE=0 in sleep mode (no matter WDTE is 1 or 0), the internal RC Timer stops for power saving. In
other words, user keeps the WDT/WKT alive in Sleep Mode by setting WKTIE=1. If the WDTE=1 and
WKTIE=0, WDT/WKT timer will be cleared and stopped to power saving in sleep mode. If the WDTE=1
and WKTIE=1, WDT/WKT timer keeps counting in sleep/normal mode. Refer to the following table and
figure.
nRESET
XRSTE
Power On
Reset
Low
Voltage
Detector
WKTIE
4
WDTE
EN
Watchdog
RC-OSC
WDTE
CLR
WDT/WKT
Timer
D
Q
RN
WKTIE
“CLRWDT”
Wake Up Timer
Interrupt
Time Out
System
Reset
WKTPSC[1:0]
“PWRDOWN”
SLEEP_ MODE
2
LVR[1:0]
System
Clock
VDD
VDD
EN
Oscillator
SLEEP_ MODE
VDD
2
SLEEP_ MODE
SLEEP_MODE
WDTE
WKTIE
SLEEP_ MODE
If the user program needs the MCU totally shuts down for power conservation in sleep mode, the
following setting of control bits should be followed.
Mode
WDTE
WKTIE
Watchdog RC Oscillator
Normal Mode
0
0
Stop
0
1
Run
1
0
1
1
Sleep Mode
0
0
Stop
0
1
Run
1
0
Stop
1
1
Run