HT82K74E datasheet(12/56 Pages) HOLTEK

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HT82K74E/HT82K74EE

Rev. 1.00

December 15, 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 two sections, the first of

these is an area of RAM where special function registers

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 di-

rectly 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.

Structure

The two sections of Data Memory, the Special Purpose

and General Purpose Data Memory are located at con-

secutive locations. All are implemented in RAM and are

8-bit wide. The start address of the Data Memory for all

devices is the address

²00H². Registers which are com-

mon to all microcontrollers, such as ACC, PCL, etc.,

have the same Data Memory address.

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.

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 readable and

writeable but some are protected and are readable only,

the details of which are located under the relevant Spe-

cial Function Register section. Note that for locations

that are unused, any read instruction to these addresses

will return the value

²00H².

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

9 F H

3 F H

Data Memory Structure

Note:

Most of the Data Memory bits can be directly

manipulated using the

²SET [m].i² and ²CLR

[m].i

² with the exception of a few dedicated bits.

The Data Memory can also be accessed

through the memory pointer register, MP.

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

0 1 H

0 2 H

0 3 H

0 4 H

0 5 H

0 6 H

0 7 H

0 8 H

0 9 H

0 A H

0 B H

0 C H

0 D H

0 E H

0 F H

1 0 H

1 1 H

1 2 H

1 3 H

1 4 H

1 5 H

1 6 H

1 7 H

1 8 H

1 9 H

1 A H

1 B H

1 C H

1 D H

1 E H

1 F H

: U n u s e d ,

r e a d a s " 0 0 "

9 F H

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

D a t a M e m o r y

( 9 6 B y t e s )

I A R

M P

A C C

P C L

T B L P

T B L H

W D T S

S T A T U S

I N T C

T M R H

T M R L

T M R C

P T R

P A

P A C

P B

P B C

P C

P C C

P D

P D C

P E

P E C

W S R

C T L R

T B H P

O S C C

R F C T R

4 0 H

2 0 H

2 1 H

Special Purpose Data Memory Structure

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