8085 is a Microprocessor which was developed by Intel in 1970s. All the instructions in this microprocessor are encoded in a single byte. Some of the instructions are followed by one or two bytes of data, which can be a memory address, an immediate operand or a port number.

In this post, we will write a program in 8085 to convert binary number to binary coded decimal(BCD) without using DAA operation.

Algorithm

Start
Clear D and E registers to account for hundreds and tens
Load data in A
Compare A with 64H
If CS = 1 go to 9
A <- A - 64H
E <- E + 1
Go to 4
Compare A with 0AH
if CS = 1 go to 14
A <- A - 0AH
D <- D + 1
go to 
C <- A
A <- D
Rotate left A 4 times
Combine unit and tens to form lower bit result
Save hundreds as upper bits and combined result as lower bit
Stop

Flow Chart

Program

      MVI E, 00H
      MOV D, E
      LDA 2100H
HUND: CPI 64H
      JC TEN
      SUI 64H
      INR E
      JMP HUND
TEN:  CPI 0AH
      JC UNIT
      SUI 0AH
      INR D
      JMP TEN
UNIT: MOV C, A
      MOV A, D
      RLC
      RLC
      RLC
      RLC
      ADD C
      STA 2101H
      MOV A, E
      STA 2102H
      RST-5

Example

2100H: FF
2101H: 55  ->  lower bits
2105H: 02  ->  upper bits
// output is 255

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