Rev. 1.20
�8
�an�a�� 2�� 201�
Rev. 1.20
�9
�an�a�� 2�� 201�
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
CTRL Register
Bit
7
6
5
4
3
2
1
0
Name
FSYSON
—
HIRCS1
HIRCS0
LXTLP
LVRF
D1
WRF
R/W
R/W
—
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
—
0
0
0
x
0
0
"x" �nknown
Bit 7
FSYSON
:
f
SYS
Control in IDLE Mode
Describe elsewhere
Bit 6
Unimplemented, read as
"
0
"
B
it
5~
4
HIRCS1~HIRCS0
: HIRC frequency clock select
Describe elsewhere
Bit
3
LXTLP
: LXT low power control
Describe elsewhere
Bit 2
LVRF
:
LVR function reset flag
Describe elsewhere
Bit 1
Undefined bit
This bit can be read or written by user software program
Bit 0
WRF
: WDT Control register software reset flag
0: Not occur
1: Occurred
This bit is set high by the WDT Control register software reset and cleared by the
application program. Note that this bit can only be cleared to zero by the application
program.
Watchdog Timer Operation
The Watchdog Timer operates by providing a device reset when its timer overflows. This means
that in the application program and during normal operation the user has to strategically clear the
Watchdog Timer before it overflows to prevent the Watchdog Timer from executing a reset. This is
done using the clear watchdog instructions. If the program malfunctions for whatever reason, jumps
to an unknown location, or enters an endless loop, the clear WDT instruction will not be executed in
the correct manner, in which case the Watchdog Timer will overflow and reset the device. There are
five bits, WE4~WE0, in the WDTC register to enable the WDT function. When the WE4~WE0 bits
value is equal to 01010B or 10101B, the WDT function is enabled. However, if the WE4~WE0 bits
are changed to any other values except 01010B and 10101B, which is caused by the environmental
noise, it will reset the microcontroller after 2~3 LIRC clock cycles. After power on these bits will
have a value of 01010B.
Under normal program operation, a Watchdog Timer time-out will initialise a device reset and set
the status bit TO. However, if the system is in the SLEEP or IDLE Mode, when a Watchdog Timer
time-out occurs, the TO bit in the status register will be set and only the Program Counter and Stack
Pointer will be reset. Three methods can be adopted to clear the contents of the Watchdog Timer.
The first is a WDT software reset, which means a certain value is written into the WE4~WE0 bit
filed except 01010B and 10101B, the second is using the Watchdog Timer software clear instruction
and the third is via a HALT instruction.
There is only one method of using software instruction to clear the Watchdog Timer. That is to use
the single "CLR WDT" instruction to clear the WDT.
The maximum time-out period is when the 2
18
division ratio is selected. As an example, with a 32
kHz LIRC oscillator as its source clock, this will give a maximum watchdog period of around 8
seconds for the 2
18
division ratio, and a minimum timeout of 7.8ms for the 2
8
division ration.
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 ...