HT56R656 datasheet(21/108 Pages) HOLTEK

21 / 108 page

HT56R62/HT56R65

HT56R642/HT56R644/HT56R654/HT56R656

Rev. 1.00

July 20, 2009

Data Memory

The Data Memory is a volatile area of 8-bit wide RAM

internal memory and is the location where temporary in-

formation is stored. Divided into three sections, the first

of these is an area of RAM where special function regis-

ters are located. These registers have fixed locations

and are necessary for correct operation of the device.

Many of these registers can be read from and written to

directly under program control, however, some remain

protected from user manipulation. The second area of

Data Memory is reserved for general purpose use. All

locations within this area are read and write accessible

under program control. The third area is reserved for the

LCD Memory. This special area of Data Memory is

mapped directly to the LCD display so data written into

this memory area will directly affect the displayed data.

The addresses of the LCD Memory area overlap those

in the General Purpose Data Memory area. Switching

between the different Data Memory banks is achieved

by setting the Bank Pointer to the correct value.

Structure

The Data Memory is subdivided into several banks, all

of which are implemented in 8-bit wide RAM. The Data

Memory located in Bank 0 is subdivided into two sec-

tions, the Special Purpose Data Memory and the Gen-

eral Purpose Data Memory.

The start address of the Data Memory for all devices is

the address

²00H². Registers which are common to all

microcontrollers, such as ACC, PCL, etc., have the

same Data Memory address. The LCD Memory is

mapped into Bank. Banks 2 to 6 contain only General

Purpose Data Memory for those devices with larger

Data Memory capacities. As the Special Purpose Data

Memory registers are mapped into all bank areas, they

can subsequently be accessed from any bank location.

General Purpose Data Memory

All microcontroller programs require an area of

read/write memory where temporary data can be stored

and retrieved for use later. It is this area of RAM memory

that is known as General Purpose Data Memory. This

area of Data Memory is fully accessible by the user pro-

gram for both read and write operations. By using the

²SET [m].i² and ²CLR [m].i² instructions individual bits

can be set or reset under program control giving the

user a large range of flexibility for bit manipulation in the

Data Memory. For devices with larger Data Memory ca-

pacities, the General Purpose Data Memory, in addition

to being located in Bank 0, is also stored in Banks 2 to 6,

the actual number of banks present depends upon the

device selected.

Special Purpose Data Memory

This area of Data Memory is where registers, necessary

for the correct operation of the microcontroller, are

stored. Most of the registers are both read and write type

but some are protected and are read only, the details of

which are located under the relevant Special Function

any read instruction to these addresses will return the

value

²00H². The Special Function registers are

mapped into all banks and can therefore be accessed

from any bank location.

G e n e r a l P u r p o s e

D a t a M e m o r y

S p e c i a l P u r p o s e

D a t a M e m o r y

0 0 H

4 0 H

F F H

3 F H

B a n k 0

B a n k 2

B a n k 1

L C D

M e m o r y

B a n k 3

B a n k 6

Data Memory Structure

HT56R656 数据表(PDF) 21 Page - Holtek Semiconductor Inc

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