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Rev. 1.20
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Rev. 1.20
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HT69F30A/HT69F40A/HT69F50A
TinyPower
TM
I/O Flash 8-Bit MCU with LCD & EEPROM
HT69F30A/HT69F40A/HT69F50A
TinyPower
TM
I/O Flash 8-Bit MCU with LCD & EEPROM
SMOD1 Register
Bit
7
6
5
4
3
2
1
0
Name
FSYS�N
—
—
—
—
LVRF
LRF
WRF
R/W
R/W
—
—
—
—
R/W
R/W
R/W
P�R
0
—
—
—
—
x
0
0
“x” unknown
Bit 7
FSYSON:
f
SYS
Control in IDLE Mode
Described elsewhere.
Bit 6~3
Unimplemented, read as "0"
Bit 2
LVRF:
LVR function reset flag
Described elsewhere.
Bit 1
LRF:
LVR Control register software reset flag
Described elsewhere.
bit 0
WRF:
WDT Control register software reset flag
0: Not occurred
1: Occurred
This bit is set to 1 by the WDT Control register software reset and cleared by the
application program. Note that this bit can only be cleared to 0 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, these clear instructions will not be executed
in the correct manner, in which case the Watchdog Timer will overflow and reset the device. The
Watchdog Timer function is determined using a configuration option. With regard to the Watchdog
Timer enable/disable function, there are also five bits, WE4~WE0, in the WDTC register to offer
the additional enable/disable control and reset control of the Watchdog Timer. If the WDT function
configuration option is determined that the WDT function is always enabled, the WE4~WE0 bits
still have effects on 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 f
SUB
clock cycles. If the WDT function configuration option is determined
that the WDT function is controlled by the WDTC control register using the application program,
the WE4~WE0 values can determine which mode the WDT operates in. The WDT function will
be disabled when the WE4~WE0 bits are set to a value of 10101B while the WDT function will
be enabled if the WE4~WE0 bits are equal to 01010B. If the WE4~WE0 bits are set to any other
values, other than 01010B and 10101B, it will reset the device after 2~3 f
SUB
clock cycles. After
power on these bits will have a value of 01010B.
WDT Function Control
WE4~WE0 Bits
WDT Function
Appli�ation P�og�am Ena�led
10101B
Disa�le
01010B
Ena�le
Any othe� value
Reset MCU
Always Ena�led
01010B o� 10101B
Ena�le
Any othe� value
Reset MCU
Watchdog Timer Enable/Disable Control