Q. Write an 8085 program and draw a flowchart to Subtract two 8-bit numbers along with considering the borrow.(8085 Microprocessor Program)
|2000||LXI||H, 3000H||21||Load H-L pair with address 3000H.|
|2003||MOV||A, M||7E||Move the 1st operand from memory to reg. A.|
|2004||INX||H||23||Increment H-L pair.|
|2005||MOV||B, M||46||Move the 2nd operand from memory to reg. B.|
|2006||MVI||C, 00H||0E||Initialize reg. C with 00H.|
|2008||SUB||B||90||Subtract B from A.|
|2009||JNC||200D||D2||Jump to address 200DH if there is no borrow.|
|200C||INR||C||0C||Increment reg. C.|
|200D||INX||H||23||Increment H-L pair.|
|200E||MOV||M, A||77||Move the result from reg. A to memory.|
|200F||INX||H||23||Increment H-L pair.|
|2010||MOV||M, C||71||Move borrow from reg. C to memory.|
- This program subtracts two operands stored in memory location 3000H and 3001H, along with considering the borrow took (if any).
- Let us assume that the operands stored at memory location 3000H is 05H and 3001H is 02H.
- Initially, H-L pair is loaded with the address of first memory location.
- The first operand is moved to accumulator from memory location 3000H and H-L pair is incremented to point to next memory location.
- The second operand is moved to register B from memory location 3001H.
- Register C is initialized to 00H. It stores the borrow (if any).
- The two operands stored in register A and B are subtracted and the result is stored in the accumulator.
- Then, carry flag is checked for borrow. If there is a borrow, C register is incremented.
- H-L pair is incremented and the result is moved from the accumulator to memory location 3002H.
- H-L pair is again incremented and borrow (either 0 or 1) is moved from register C to memory location 3003H.