HT46R46 datasheet(13/77 Pages) HOLTEK

13 / 77 page

HT46R46/C46/R47/C47/R48A/C48A/R49

Rev. 1.30

June 5, 2008

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 bits wide but the length of each memory section is dic-

tated by the type of microcontroller chosen. The start

address of the Data Memory for all devices is the ad-

dress

²00H². Registers which are common 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

writable 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.

Special Function Registers

To ensure successful operation of the microcontroller,

certain internal registers are implemented in the Data

Memory area. These registers ensure correct operation

of internal functions such as timers, interrupts, etc., as

well as external functions such as I/O data control and

A/D converter operation. The location of these registers

within the Data Memory begins at the address 00H. Any

unused Data Memory locations between these special

function registers and the point where the General Pur-

pose Memory begins is reserved for future expansion

purposes, attempting to read data from these locations

will return a value of 00H.

Indirect Addressing Register - IAR

The IAR register, located at Data Memory address

²00H², is not physically implemented. This special regis-

ter allows what is known as indirect addressing, which

permits data manipulation using Memory Pointers in-

stead of the usual direct memory addressing method

where the actual memory address is defined. Any ac-

tions on the IAR register will result in corresponding

read/write operations to the memory location specified

by the Memory Pointer MP. Reading the IAR register in-

directly will return a result of

²00H² and writing to the

Memory Pointer - MP

One Memory Pointer, known as MP, is physically imple-

mented in Data Memory. The Memory Pointer can be

written to and manipulated in the same way as normal

registers providing an easy way of addressing and

tracking data. When using any operation on the indirect

addressing register IAR, it is actually the address speci-

fied by the Memory Pointer that the microcontroller will

be directed to.

For devices with 64 or 88 bytes of RAM Data Memory,

bit 7 of the Memory Pointer is not implemented. How-

ever, it must be noted that when the Memory Pointer for

these devices is read, bit 7 will be read as high.

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

B F H

3 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

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

7 F H

3 F H

H T 4 6 R 4 6 a n d H T 4 6 R 4 7

H T 4 6 R 4 9

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

2 8 H

7 F H

2 7 H

H T 4 6 R 4 8 A

Data Memory Structure

Note:

Most of the Data Memory bits can be directly manipulated using the

²SET [m].i² and ²CLR [m].i² with the excep-

tion of a few dedicated bits. The Data Memory can also be accessed through the memory pointer register MP.

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