Rev. 1.40
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Rev. 1.40
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BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
Watchdog Timer
The Watchdog Timer is provided to prevent program malfunctions or sequences from jumping to
unknown locations, due to certain uncontrollable external events such as electrical noise.
Watchdog Timer Clock Source
The Watchdog Timer clock source is provided by the internal RC oscillator, f
LIRC
. The LIRC internal
oscillator has an approximate frequency of 32 kHz and this specified internal clock period can vary
with V
DD
, temperature and process variations. The Watchdog Timer source clock is then subdivided
by a ratio of 2
8
to 2
18
to give longer timeouts, the actual value being chosen using the WS2~WS0
bits in the WDTC register.
Watchdog Timer Control Register
A single register, WDTC, controls the required timeout period as well as the enable/disable
operation. This register controls the overall operation of the Watchdog Timer.
WDTC Register
Bit
7
6
5
4
3
2
1
0
Name
WE4
WE3
WE�
WE1
WE0
WS�
WS1
WS0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
1
0
1
0
0
1
1
Bit 7~3
WE4~WE0
: WDT function enable control
10101 or 01010: Enabled
Other values: Reset MCU
If these bits are changed due to adverse environmental conditions, the microcontroller
will be reset. The reset operation will be activated after 2~3 LIRC clock cycles and the
WRF bit in the RSTFC register will be set to 1.
Bit 2~0
WS2~WS0
: WDT time-out period selection
000: 2
8
/f
LIRC
001: 2
10
/f
LIRC
010: 2
12
/f
LIRC
011: 2
14
/f
LIRC
100: 2
15
/f
LIRC
101: 2
16
/f
LIRC
110: 2
17
/f
LIRC
111: 2
18
/f
LIRC
These three bits determine the division ratio of the watchdog timer source clock,
which in turn determines the time-out period.