Rev. 1.10
46
November 26, 2019
Rev. 1.10
47
November 26, 2019
HT68FB240
USB Low Speed Flash MCU
CTRL Register
Bit
7
6
5
4
3
2
1
0
Name
FSYSON
—
—
—
—
LVRF
LRF
WRF
R/W
R/W
—
—
—
—
R/W
R/W
R/W
POR
0
—
—
—
—
x
0
0
"x" unknown
Bit 7
FSYSON:
f
SYS
Control in IDLE Mode
0: disable
1: enable
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 occur
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. With regard to
the Watchdog Timer enable/disable function, there are five bits, WE4~WE0, in the WDTC register
to offer additional enable/disable and reset control of the Watchdog Timer.
WDT Enable/Disabled using the WDT Control Register
The WDT is enabled/disabled using the WDT control register, the WE4~WE0 values can determine
which mode the WDT operates in. The WDT will be disabled when the WE4~WE0 bits are set to a
value of 10101B. The WDT function will be enabled if the WE4~WE0 bit value is 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 LIRC clock cycles. After power on these bits will have the value of 01010B.
WDT Configuration Option
WE4~WE0 Bits
WDT Function
Controlled by WDT Control Register
10101B
Disable
01010B
Enable
Any other value
Reset MCU
Watchdog Timer Enable/Disable Control
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 reset, which means a certain value except 01010B and 10101B written into the
WE4~WE0 bit filed, the second is using the Watchdog Timer software clear instructions and the