HT46R74D-1 Holtek Semiconductor, HT46R74D-1 Datasheet - Page 29

• Manufacturer Part Number: HT46R74D-1
• Description: Dual Slope A/D Type MCU
• Manufacturer: Holtek Semiconductor

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Low Voltage Reset/Detector Functions
There is a low voltage detector, LVD, and a low voltage
r e s et c i r c ui t, LV R, i mpl ement ed wi th in the
microcontroller. These two functions can be en-
abled/disabled via configuration options. Once the LVD
option is enabled, the user can use the RTCC.3 bit to
enable/disable the LVD circuit and read the LVD detec-
tor status from the RTCC.5 bit. Otherwise the LVD func-
tion is disabled.
The RTCC register definitions are listed below.
The LVR has the same effect or function as the external
RES signal which performs a device reset. When in the
Power Down Mode, both the LVR and LVD are disabled.
The microcontroller provides a low voltage reset circuit
in order to monitor the supply voltage of the device. If the
supply voltage of the device is within the range
0.9V~V
a battery, the LVR will automatically reset the device in-
ternally.
Note: *1: To make sure that the system oscillator has stabilised, the SST provides an extra delay of 1024 system
Rev. 1.10
Bit No.
0~2
6~7
*2: Since a low voltage state has to be maintained in its original state for over 1ms, therefore after the 1ms delay,
LVR
3
4
5
, such as what might happen when changing
clock pulses before entering normal operation.
the device enters the reset mode.
RT0~RT2
QOSC
LVDO
Label
LVDC
8 to 1 multiplexer control inputs to select the real clock prescaler output
LVD enable/disable (1/0)
32768Hz OSC quick start-up function
0/1: quick/slow start
LVD detect output (1/0)
1: low voltage detect, read only
Unused bit, read as 0
RTCC (09H) Register
Low Voltage Reset
29
When the LVD function configuration option is set to the
enable state, the LVD voltage option will decide the de-
tecting voltage. When the LVD configuration option is
set to LVR+0.3, the actual LVD voltage depends upon
the LVR options and will detect the VDD voltage. When
LVD option is set to Regulator+ 0.2, the actual LVD volt-
age is set to VLVD3 (defined in the DC characteristics
section), and will detect the regulator input voltage.
The LVR includes the following specifications:
The low voltage, which is specified as 0.9V~V
to remain within this range for a period of time greater
than 1ms. If the low voltage state does not exceed
1ms, the LVR will ignore it will not perform a reset
function.
The LVR has an OR function with the external RES
signal to perform a device reset.
Function
HT46R74D-1
January 11, 2007
LVR
, has