
Rev. 1.20
52
November 20, 2019
Rev. 1.20
53
November 20, 2019
HT66F2740
12V High Current Flash MCU
HT66F2740
12V High Current Flash MCU
the supply voltage of the device drops to within a range of 0.9V~V
LVR
such as might occur when
changing the battery in battery powered applications, the LVR will automatically reset the device
internally and the LVRF bit in the RSTFC register will also be set to 1. For a valid LVR signal, a
low supply voltage, i.e., a voltage in the range between 0.9V~V
LVR
must exist for a time greater
than that specified by t
LVR
in the LVR/LVD Electrical Characteristics. If the low supply voltage
state does not exceed this value, the LVR will ignore the low supply voltage and will not perform
a reset function. The actual V
LVR
value can be selected by the LVS bits in the LVRC register. If the
LVS7~LVS0 bits are changed to some different values by environmental noise, the LVR will reset
the device after a delay time, t
SRESET
. When this happens, the LRF bit in the RSTFC register will be
set to 1. After power on the register will have the value of 01010101B. Note that the LVR function
will be automatically disabled when the device enters the SLEEP or IDLE mode.
LVR
Internal Reset
t
RSTD
+ t
SST
Low Voltage Reset Timing Chart
• LVRC Register
Bit
7
6
5
4
3
2
1
0
Name
LVS7
LVS6
LVS5
LVS4
LVS3
LVS2
LVS1
LVS0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
1
0
1
0
1
0
1
Bit 7~0
LVS7~LVS0
: LVR Voltage Select control
01010101: 2.1V
00110011: 2.55V
10011001: 3.15V
10101010: 3.8V
Any other value: Generates MCU reset – register is reset to POR value
When an actual low voltage condition occurs, as specified by one of the four defined
LVR voltage values above, an MCU reset will be generated. The reset operation
will be activated after the low voltage condition keeps more than a t
LVR
time. In this
situation the register contents will remain the same after such a reset occurs.
Any register value, other than the four defined LVR values above, will also result in
the generation of an MCU reset. The reset operation will be activated after a delay
time, t
SRESET
. However in this situation the register contents will be reset to the POR
value.
• RSTFC Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
LVRF
LRF
WRF
R/W
—
—
—
—
—
R/W
R/W
R/W
POR
—
—
—
—
—
x
0
0
“x”: unknown
Bit 7~3
Unimplemented, read as “0”
Bit 2
LVRF
: LVR function reset flag
0: Not occur
1: Occurred
This bit is set to 1 when a specific Low Voltage Reset situation condition occurs. This
bit can only be cleared to 0 by the application program.