Rev. 1.00
54
September 11, 2018
Rev. 1.00
55
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC 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 sourced from the LIRC oscillator. 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 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
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
10101: Disable
01010: Enable
Other values: Reset MCU
When these bits are changed by the environmental noise or software setting to reset
the microcontroller, the reset operation will be activated
after a delay time, t
SRESET
, 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 timeout period.
• RSTFC Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
RSTF
LVRF
LRF
WRF
R/W
—
—
—
—
R/W
R/W
R/W
R/W
POR
—
—
—
—
0
x
0
0
"x": unknown
Bit 7~4
Unimplemented, read as "0"
Bit 3
RSTF
: Reset control register software reset flag
Refer to the RES Pin Reset section.
Bit 2
LVRF
: LVR function reset flag
Refer to the Low Voltage Reset section.