HT56R64 datasheet(21/90 Pages) HOLTEK

21 / 90 page

HT56R64

Rev. 1.40

September 8, 2009

V D D

R e a d D a t a R e g i s t e r

C o n t r o l B i t

D a t a B u s

W r i t e C o n t r o l R e g i s t e r

C h i p R e s e t

R e a d C o n t r o l R e g i s t e r

W r i t e D a t a R e g i s t e r

D a t a B i t

P B 0 / A N 0 ~ P B 7 / A N 7

A C S 2 ~ A C S 0

T o A / D C o n v e r t e r

P C R 2

P C R 1

P C R 0

W e a k

P u l l - u p

A n a l o g

I n p u t

S e l e c t o r

C K

P u l l - H i g h

R e g i s t e r

S e l e c t

PB Input/Output Ports

Liquid Crystal Display (LCD) Driver

For large volume applications, which incorporate an

LCD in their design, the use of a custom display rather

than a more expensive character based display reduces

costs significantly. However, the corresponding signals

required, which vary in both amplitude and time, to drive

such a custom display require many special consider-

ations for proper LCD operation to occur. The Holtek

LCD Driver function, with its internal LCD signal gener-

ating circuitry and various options, will automatically

generate these time and amplitude varying signals to

provide a means of direct driving and easy interfacing to

a range of custom LCDs.

LCD Memory

An area of Data Memory is especially reserved for use

by the LCD data. This data area is known as the LCD

Memory. Any data written here will be automatically

read by the internal LCD driver circuits, which will in turn

automatically generate the necessary LCD driving sig-

nals. Therefore any data written into the LCD Memory

will be immediately reflected into the actual LCD display

connected to the microcontroller. The start address of

the LCD Memory is 40H; the end address of the LCD

Memory is 60H.

As the LCD Data Memory addresses overlap those of

the General Purpose Data Memory, the LCD Data Mem-

ory is stored in its own memory data bank, which is dif-

ferent from that of the General Purpose Data Memory.

The LCD Data Memory is stored in Bank 1. The Data

Memory Bank is chosen by using the Bank Pointer,

which is a special function register in the Data Memory,

with the name, BP. When the lowest bit of the Bank

Pointer has the binary value

²0², only the General Pur-

pose Data Memory will be accessed, no read or write

actions to the LCD Memory will take place. To access

the LCD Memory therefore requires first that Bank 1 is

selected by setting the lowest bit of the Bank Pointer to

the binary value

²1². After this, the LCD Memory can

then be accessed by using indirect addressing through

the use of Memory Pointer MP1. With Bank 1 selected,

then using MP1 to read or write to the memory area,

40H~60H, will result in operations to the LCD Memory.

Directly addressing the LCD Memory is not applicable

and will result in a data access to the Bank 0 General

Purpose Data Memory.

The diagrams below are based on 33

´2, 33´3or32´4

format pixel drive capability LCD panels. The 4-COM for-

mat will be automatically setup when the 1/4 duty control

bit is selected while the 3-COM format will be automati-

cally setup if the 1/3 duty control bit is selected.

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