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October 04, 2011

Written by @ Pradip Yadav

Aim: Write an ALP to reverse the bits of a byte and store the reversed bit at external memory 4500H.

Apparatus Used: Micro-controller kit.

Assumption: Suppose a byte is stored at 4000H and we have reversed its bit.

12=0001 0010 after reversing it will become

48=0100 1000

Algorithm:

· Initialize the location to store the byte.
· Initialize a Register R1 to store output.
· Initialize the counter as the number of bits.
· Get byte into the Accumulator.
· Rotate the content of accumulator left with carry.
· Exchange the content of accumulator to register R1.
· Rotate the content of accumulator right with carry.
· Exchange the content of accumulator to register R1 again.
· Repeat the process till counter is reset.
· Finally move the content of R1 into Register A and store reversed number at 4500H.

Program:

Description of used instruction:

MOV: Used for Load and Copy the Data. This copies a byte from the source location to destination.

DJNZ: In this instruction a byte is decremented, and if result is not zero it will jump to the target address.

MOVX: This instruction transfer data between external memory and register A.

DPTR: This is Data Pointer. It is used for containing 16 bit data or memory address.

SJMP: Short Jump loop is used for indefinite loop within program basically used to end the program.

INC: This instruction adds 1 to the register or memory location specified by the operand.

RLC: Rotate accumulator left with carry.

RRC: Rotate accumulator Right with carry.

XCH: Exchange the content of accumulator with register.

Result:

Input: 4000-12 (0001 0010)

Output: 4500-48 (0100 1000)

Procedure to find output:

· After ending (SJMP) the program, press Enter two times.

· You will get message “Welcome to ------KIT”.

· Press G and Provide initial address of program as in this program, starting address is 3000 H.

· Press Enter.

· After pressing Enter, You will get Message “Execution Completed”.

· Press Reset on micro-controller KIT.

· Press M and You will get Message “Enter Address”.

· Provide Location of Input as in this program 4000H. Press Space and write a number.

· Press Enter two times again.

· Press G and provide starting address and Press Enter.

· You will Get Message “Execution Completed”.

· Press M and You will Get Message “Enter Address”.

· Provide Address for Output as in this Program 4500H and Press Space and you get Output and so on.