Addressing Modes in Microprocessor (8051/8085) with Examples

• Immediate: Data in instruction. MOV A,#25H, MVI A,30H
• Register: Operands in registers. MOV A,R0, ADD A,R1, MOV A,B
• Direct: 8-bit direct address. MOV A,30H (internal RAM/SFR), STA 2500H
• Register Indirect: Address in register pair. MOV A,@R0, LDAX B, MOVX A,@DPTR
• Indirect (via memory pointer): MOV A,@A+DPTR (indexed)
• Indexed: Base+index e.g., MOVC A,@A+DPTR, MOVC A,@A+PC
• Relative: PC+offset SJMP -10H, JC LOOP
• Absolute: 11/16-bit address LJMP 1000H, AJMP LOOP
• Bit: Bit addressable SETB P1.0, CLR 20H.3
• Implied: NOP, CPL A

Each mode defines how effective address/data is fetched.