Sunday, September 13, 2009

2-Digit BCD to binary conversion(8085)

Statement: Convert a 2-digit BCD number stored at memory address 2200H into its binary equivalent number and store the result in a memory location 2300H.

Sample Problem
(2200H) = 67H
(2300H) = 6 x OAH + 7 = 3CH + 7 = 43H
Source Program:
LDA 2200H : Get the BCD number
MOV B, A : Save it
ANI OFH : Mask most significant four bits
MOV C, A : Save unpacked BCDI in C register
MOV A, B : Get BCD again
ANI FOH : Mask least significant four bits
RRC : Convert most significant four bits into unpacked BCD2
MOV B, A : Save unpacked BCD2 in B register
XRA A : Clear accumulator (sum = 0)
MVI D, 0AH : Set D as a multiplier of 10
Sum: ADD D : Add 10 until (B) = 0
DCR B : Decrement BCD2 by one
JNZ SUM : Is multiplication complete? i if not, go back and add again
ADD C : Add BCD1
STA 2300H : Store the result
HLT : Terminate program execution

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