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Rev. 1.10
44
March 02, 2020
Rev. 1.10
45
March 02, 2020
BS83A02L/BS83B04L
Ultra-Low Power Touch Key Flash MCU
BS83A02L/BS83B04L
Ultra-Low Power Touch Key Flash MCU
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 clock, f
WDT
, which is supplied by the
LIRC oscillator with the output frequency of f
LIRC
/8. The LIRC internal oscillator has an approximate
frequency of 2kHz 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
5
to 2
11
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 and reset
operation.
• WDTC Register
Bit
7
6
5
4
3
2
1
0
Name
WE4
WE3
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
01010/10101: Enable
Other values: Reset MCU
When these bits are changed to any other values due to environmental noise the
microcontroller will be reset; this reset operation will be activated after a delay time,
t
SRESET
and the WRF bit in the RSTFC register will be set high.
Bit 2~0
WS2~WS0
: WDT time-out period selection
000: 2
5
/f
WDT
001: 2
5
/f
WDT
010: 2
6
/f
WDT
011: 2
7
/f
WDT
100: 2
8
/f
WDT
101: 2
9
/f
WDT
110: 2
10
/f
WDT
111: 2
11
/f
WDT
These three bits determine the division ratio of the Watchdog Timer source clock,
which in turn determines the timeout period. The internal clock, f
WDT
is supplied by the
LIRC oscillator with the output frequency of f
LIRC
/8.
• RSTFC Register – BS83A02L
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
LVRF
LRF
WRF
R/W
—
—
—
—
—
R/W
R/W
R/W
POR
—
—
—
—
—
x
0
0
“x”: Unknown
Bit 7~3
Unimplemented, read as “0”
Bit 2
LVRF
: LVR function reset flag
Refer to the Low Voltage Reset section.
Bit 1
LRF
: LVR control register software reset flag
Refer to the Low Voltage Reset section.