Watchdog Timer; Watchdog Timer Clock Source; Watchdog Timer Control Register - Holtek BS83A04C Manual

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
the LIRC oscillator. The LIRC internal oscillator has an approximate frequency of 32kHz and this
specified internal clock period can vary with V
Timer source clock is then subdivided by a ratio of 2
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
Name WE4
R/W R/W
POR 0
WE4~WE0: WDT function software control
Bit 7~3
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
Bit 2~0 WS2~WS0: WDT time-out period selection
000: 2
001: 2
010: 2
011: 2
100: 2
101: 2
110: 2
111: 2
These three bits determine the division ratio of the Watchdog Timer source clock,
which in turn determines the timeout period.
• RSTFC Register
Bit 7
Name —
R/W —
POR —
Bit 7~4 Unimplemented, read as "0"
Bit 3 RSTF: Reset control register software reset flag
Describe elsewhere.
Bit 2 LVRF: LVR function reset flag
Described elsewhere.
Rev. 1.00
4-Key Enhanced Touch I/O Flash MCU
, temperature and process variations. The Watchdog
DD
6 5 4
WE3 WE2 WE1
R/W R/W R/W
1 0 1
and the WRF bit in the RSTFC register will be set high.
/f
8
LIRC
/f
10
LIRC
/f
12
LIRC
/f
14
LIRC
/f
15
LIRC
/f
16
LIRC
/f
17
LIRC
/f
18
LIRC
6 5 4
— — —
— — —
— — —
40
which is sourced from
LIRC
to 2 to give longer timeouts, the actual value
8 18
3 2 1
WE0 WS2 WS1
R/W R/W R/W
0 0 1
3 2 1
RSTF LVRF —
R/W R/W —
0 x —
BS83A04C
0
WS0
R/W
1
0
WRF
R/W
0
"x": Unknown
March 24, 2020