HT82B40A datasheet(10/54 Pages) HOLTEK

10 / 54 page

HT82B40R/HT82B40A

Rev. 1.70

November 5, 2014

tempreg1 db

; temporary register #1

tempreg2 db

; 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

²F06H² 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

²F05H² transferred to tempreg2 and TBLH

; in this example the data

²1AH² is transferred to

; tempreg1 and data

²0FH² to register tempreg2

; the value

²00H² will be transferred to the high byte register TBLH

org F00h

; sets initial address of last page

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

Because the TBLH register is a read-only register and

cannot be restored, care should be taken to ensure its

protection if both the main routine and Interrupt Service

Routine use the table read instructions. If using the table

read instructions, the Interrupt Service Routines may

change the value of TBLH and subsequently cause er-

rors if used again by the main routine. As a rule it is rec-

ommended that simultaneous use of the table read

instructions should be avoided. However, in situations

where simultaneous use cannot be avoided, the inter-

rupts should be disabled prior to the execution of any

main routine table-read instructions. Note that all table

related instructions require two instruction cycles to

complete their operation.

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 bits 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.

0 0 H

4 0 H

D F H

3 F H

S p e c i a l

P u r p o s e

D a t a

M e m o r y

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

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.

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