HT95R25 datasheet(10/51 Pages) HOLTEK

10 / 51 page

HT95R25

Rev. 1.00

March 6, 2009

Data Memory

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

ternal 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

RAM Data Memory is reserved for general purpose use.

All locations within this area are read and write accessi-

ble under program control.

Structure

The Special Purpose and General Purpose Data Mem-

ory are located at consecutive locations. All are imple-

mented in RAM and are 8 bits wide. The start address of

the Data Memory is the address 00H. Registers which

are common to all microcontrollers, such as ACC, PCL,

etc., have the same Data Memory address. Note that af-

ter power-on, the contents of the Data Memory, will be in

an unknown condition, the programmer must therefore

ensure that the Data Memory is properly initialised. The

Special Purpose Data Memory is located in Bank 0

while the General Purpose Data Memory is divided into

11 individual areas or Banks known as Bank 0 to Bank

10. Switching between different banks is achieved by

setting the Bank Pointer to the correct value.

tempreg1

; temporary register #1

tempreg2

; temporary register #2

mov a,06h

; initialise table pointer - note that this address

; is referenced

mov tblp,a

; to the last page or present page

tabrdl

tempreg1

; transfers value in table referenced by table pointer

; to tempregl

; data at prog. memory address

²3F06H² transferred to

; tempreg1 and TBLH

dec tblp

; reduce value of table pointer by one

tabrdl

tempreg2

; transfers value in table referenced by table pointer

; to tempreg2

; data at prog.memory address

²3F05H² transferred to

; tempreg2 and TBLH

; in this example the data

²1AH² is transferred to

; tempreg1 and data

²0FH² to register tempreg2

; the value

²0FH² will be transferred to the high byte

; register TBLH

org 3F00h

; sets initial address of HT95R25 last page

00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh

B a n k 1 0

0 0 H

4 0 H

F F H

3 F H

B a n k 3

B a n k 2

B a n k 1

B a n k 0

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

D a t a M e m o r y

B a n k 0

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

D a t a M e m o r y

B a n k 1 ~ 1 0

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

D a t a M e m o r y

Data Memory Structure

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