HT47C20 datasheet(30/56 Pages) HOLTEK

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HT47C20

January 18, 2000

LCD display memory

The HT47C20 provides an area of embedded

data memory for LCD display. The LCD display

memory is designed into 20´4 bits. If the LCD

selected 19´4 segments output, the 53H of the

LCD display memory can not be accessed. This

area is located from 40H to 53H of the RAM at

Bank 1. Bank pointer (BP; located at 04H of the

data memory) is the switch between the gen-

eral data memory and the LCD display mem-

ory. When the BP is set ²1² any data written

into 40H~53H will effect the LCD display (indi-

rect addressing mode using MP1). When the BP

is cleared ²0², any data written into 40H~53H

means to access the general purpose data mem-

ory. The LCD display memory can be read and

written only by indirect addressing mode using

MP1. When data is written into the display

data area, it is automatically read by the LCD

driver which then generates the corresponding

LCD driving signals. To turn the display on or

off, a ²1² or a ²0² is written to the corresponding

bit of the display memory, respectively. The fig-

ure illustrates the mapping between the dis-

play memory and LCD pattern for the

HT47C20.

LCD driver output

The output number of the HT47C20 LCD driver

can be 20´3or19´4 by mask option (i.e., 1/3 duty or 1/4

duty).

The bias type of the LCD driver is ²C² type. A ca-

pacitor mounted between C1 and C2 pins is

needed. The bias voltage of the LCD driver can be

1/2 bias or 1/3 bias by mask option. If 1/2 bias is

selected, a capacitor mounted between V3 pin

and the ground is required. If 1/3 bias is selected,

two capacitors are needed for V1 and V3 pins.

Refer to the application diagram.

40H

CO M

SEG M E N T

41H

42H

43H

51H

52H

53H

Bi t

Display memory (bank 1)

1/ 3 bi as

1/ 2 bi as

V DD

V1, V2, V3 application diagram

HT47C20 Datasheet(PDF) 30 Page - Holtek Semiconductor Inc

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