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11 Moving Data

The document discusses moving data from external and code memory in an 8051 microcontroller. It explains that the MOVX instruction is used to move data from external memory by specifying the address using the DPTR register. The MOVC instruction moves data from code memory to the accumulator by using indirect addressing with either DPTR or the PC as the data pointer. An example assembly program is provided that uses MOVC to transfer data from consecutive ROM locations from 01F0H to 01F7H to registers R0 through R7 by initializing DPTR as the base pointer and indexing the accumulator.

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60 views23 pages

11 Moving Data

The document discusses moving data from external and code memory in an 8051 microcontroller. It explains that the MOVX instruction is used to move data from external memory by specifying the address using the DPTR register. The MOVC instruction moves data from code memory to the accumulator by using indirect addressing with either DPTR or the PC as the data pointer. An example assembly program is provided that uses MOVC to transfer data from consecutive ROM locations from 01F0H to 01F7H to registers R0 through R7 by initializing DPTR as the base pointer and indexing the accumulator.

Uploaded by

Bunty
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Moving Data

External Data Moves

For the 8051 microcontroller, the MOVX (Move


External) instruction is specifically designed for
accessing external data memory. In the case of MOVX,
only indirect addressing is allowed, and you need to use
the DPTR (Data Pointer) register to specify the address
in the external memory.
Simulator Program Execution
Simulation Program MOVEX

Use Accumulator for external data


move, Use of other registers is not
valid
Simulation Program MOVX

Here you should not except to change the content of Port


P0 latch (Address 80H).
MOVX always considers external memory.
Try the program first with MOVX @R0,A and Then with
MOV @R0,A
Simulation Program MOVX

Use of direct address in MOVX is not permitted


Instead use DPTR
Simulation Program MOVX

Use of direct address in MOVX is not permitted


Instead use DPTR
External Data Moves
Code Memory Read Only Data Moves
Code Memory Read-Only Data Moves

The MOVC instruction is designed specifically for


accessing code memory and copying the data to
the accumulator, making it useful for cases where
you need to read data from code memory during
program execution.
Code Memory Read-Only Data Moves

MOVC command always uses indirect addressing


and that too only with either (1) DPTR in conjunction
with the accumulator or (2) PC in conjunction with the
accumulator as a data pointer.
Code memory ROM Data Move

Here instead of MOVC A,@DPTR


There should be MOVC A,@A+DPTR
Code memory ROM data Moves
Code memory ROM data Moves
Write an assembly language program for the 8051
microcontroller that transfers the data contained in ROM
memory (program memory) locations 01F0H to 01F7H to
registers R0 and R7.
Code memory ROM data Moves
Directly moving data from code memory to any register is not possible.
Therefore, the strategy involves initializing the base pointer in DPTR and
indexing to the accumulator. Subsequently, the program will use the MOVC
instruction (MOVC A,@A+DPTR) to copy data from ROM to the
accumulator. Following this, the data will be transferred from the
accumulator to register R0.

The same procedure will be repeated by updating the memory index in


the accumulator to access the next memory location. This process
continues iteratively, allowing data to be transferred from
consecutive memory locations to the remaining registers R1 through R7.
Data is stored from 01F0
Hence ORG 01F0H
That means organize from
01F0

Data is EA, EB, EC, ED, EF


F0, F1, F2

Hence
DB EAH, EBH, ECH……
Program is to be written
from memory location
0000.

Hence
ORG 000H
initializing base data pointer
to 0100

Hence
MOV DPTR,#0100H

(we will add base with F0 to


F7 to create addresses for
stored data as 01F0 to 01F7)
First we will move data located
at 01F0 to Accumulator using
MOVC A,@A+DPTR and then
from Accumulator to R0

We will repeat this procedure


for all other ROM locations and
move data of these ROM
locations to remaining registers
R1 to R7
Before Program Assembly
After Program Assembly
Before Program Run
After Program Run

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