Rev. 1.40
9�
De�e��e� 1�� �01�
Rev. 1.40
97
De�e��e� 1�� �01�
BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
Low Voltage Reset – LVR
The microcontroller contains a low voltage reset circuit in order to monitor the supply voltage of the
device. The LVR function is always enabled with a specific LVR voltage, V
LVR
. If the supply voltage
of the device drops to within a range of 0.9V~V
LVR
such as might occur when changing the battery,
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 LVD/LVR 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 have any other value, which may perhaps occur
due to adverse environmental conditions such as noise, the LVR will reset the device after 2~3 f
LIRC
clock cycles. 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 power down mode.
LVR
Inte�nal Reset
t
RSTD
+ t
SST
Note: t
RSTD
is power-on delay with typical time=50 ms
Low Voltage Reset Timing Chart
•
LVRC Register
Bit
7
6
5
4
3
2
1
0
Name
LVS7
LVS�
LVS�
LVS4
LVS3
LVS�
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
01010101: 2.1V
00110011: 2.55V
10011001: 3.15V
10101010: 3.8V
Other values: Generates a 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 value above, an MCU reset will generated. The reset operation will be
activated after 2~3 f
LIRC
clock cycles. In this situation the register contents will remain
the same after such a reset occurs.
Any register value, other than the four defined register values above, will also result
in the generation of an MCU reset. The reset operation will be activated after 2~3 f
LIRC
clock cycles. However in this situation the register contents will be reset to the POR
value.