HT68F13 datasheet(120/161 Pages) HOLTEK

120 / 161 page

LVD Operation

The Low Voltage Detector function operates by comparing the power supply voltage, VDD, with a

pre-specified voltage level stored in the LVDC register. This has a range of between 2.0V and 4.4V.

When the power supply voltage, VDD, falls below this pre-determined value, the LVDO bit will be set

high indicating a low power supply voltage condition. The Low Voltage Detector function is supplied

by a reference voltage which will be automatically enabled. When the device is powered down the low

voltage detector will remain active if the LVDEN bit is high. After enabling the Low Voltage Detector,

a time delay tLVDS should be allowed for the circuitry to stabilise before reading the LVDO bit. Note also

that as the VDD voltage may rise and fall rather slowly, at the voltage nears that of VLVD, there may be

multiple bit LVDO transitions.

The Low Voltage Detector also has its own interrupt which is contained within one of the

Multi-function interrupts, providing an alternative means of low voltage detection, in addition to

polling the LVDO bit. The interrupt will only be generated after a delay of tLVD after the LVDO bit has

been set high by a low voltage condition. When the device is powered down the Low Voltage Detector

will remain active if the LVDEN bit is high. In this case, the LVF interrupt request flag will be set,

causing an interrupt to be generated if VDD falls below the preset LVD voltage. This will cause the

device to wake-up from the SLEEP or IDLE Mode, however if the Low Voltage Detector wake up

function is not required then the LVF flag should be first set high before the device enters the SLEEP or

IDLE Mode.

SCOM FunctionforLCD

The devices have the capability of driving external LCD panels. The common pins for LCD driving,

SCOM0~ SCOM3, are pin shared with certain pin on the PC0~PC1 and PB6 ~ PB7 pins. The LCD

signals (COM and SEG) are generated using the application program.

LCDOperation

An external LCD panel can be driven using this device by configuring the PC0~PC1 or PB6 ~ PB7

pins as common pins and using other output ports lines as segment pins. The LCD driver function is

controlled using the SCOMC register which in addition to controlling the overall on/off function also

controls the bias voltage setup function. This enables the LCD COM driver to generate the necessary

VDD/2 voltage levels for LCD 1/2 bias operation.

HT68F13/HT68F14/HT68F15

EnhancedI/OFlashTypeMCU

Rev.1.10

120

February9,2011

V D D

V L V D

L V D E N

L V D O

t L V D S

LVD Operation

V D D

S C O M 0 ~

S C O M 3

S C O M E N

C O M n E N

V D D / 2

S C O M o p e r a t i n g c u r r e n t

LCDCOMBias

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