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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
More information regarding external reset circuits is located in Application Note HA0075E on the
Holtek website.
Pulling the RES Pin low using external hardware will also execute a device reset. In this case, as in
the case of other resets, the Program Counter will reset to zero and program execution initiated from
this point.
RES Reset Timing Chart
Note: t
RSTD
is power-on delay, typical time=16.7ms
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 SMOD1 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 A.C. 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
SUB
clock cycles.
When this happens, the LRF bit in the SMOD1 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.
Note: t
RSTD
is power-on delay, typical time=50ms
Low Voltage Reset Timing Chart