Rev. 1.20
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Rev. 1.20
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BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/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 f
S
UB
clock, depending on the devices,
the f
SUB
clock is in turn supplied by the LIRC oscillator or either the LXT or LIRC oscillator selected
by a configuration option. The LIRC internal oscillator has an approximate frequency of 32kHz and
this specified internal clock period can vary with V
DD
, temperature and process variations. The LXT
oscillator is supplied by an external 32.768 kHz crystal. 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 operation. The
WDTC register is initiated to 01010011B at any reset except WDT time-out hardware warm reset
.
WDTC Register
Bit
7
6
5
4
3
2
1
0
Name
WE4
WE�
WE2
WE1
WE0
WS2
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 software control
01010B or 10101B: Enabled
Other values: Reset MCU (Reset will be active
after
2
~3
LIRC clock for debounce time.)
If the MCU reset is caused by the WE [4:0]
in
WDTC software reset, the WRF flag of
CTRL register will
be
set.
Bit 2~ 0
WS2 ~ WS0
: WDT Time-out
p
eriod selection
000:
2
8
/f
S
UB
001:
2
10
/f
S
UB
010:
2
12
/f
S
UB
011:
2
14
/f
S
UB
100:
2
15
/f
SUB
101:
2
16
/f
SUB
110: 2
17
/f
S
UB
111: 2
18
/f
S
UB
These three bits determine the division ratio of the Watchdog Timer source clock,
which
in
turn determines the timeout period.
Содержание BS82B12A-3
Страница 33: ...Rev 1 20 33 January 23 2015 BS82B12A 3 BS82C16A 3 BS82D20A 3 Touch Key 8 Bit Flash MCU with LED LCD Driver ...
Страница 34: ...Rev 1 20 34 January 23 2015 BS82B12A 3 BS82C16A 3 BS82D20A 3 Touch Key 8 Bit Flash MCU with LED LCD Driver ...
Страница 35: ...Rev 1 20 35 January 23 2015 BS82B12A 3 BS82C16A 3 BS82D20A 3 Touch Key 8 Bit Flash MCU with LED LCD Driver ...