ADDRESSING MODE OF THE X86 ARCHITECTURE IN MICROPROCESSOR

The addressing mode indicates the manner in which the operand is presented. Register Addressing (operand address R is in the address field) mov ax, bx ; moves contents of register bx into ax Immediate (actual value is in the field) mov ax, 1 ; moves value of 1 into register ax or mov ax, 010Ch ; moves value of 0x010C into register ax Direct memory addressing (operand address is in the address field) .data my_var dw 0abcdh ; my_var = 0xabcd .code mov ax, [my_var] ; copy my_var content into ax (ax=0xabcd) Direct offset addressing (uses arithmetics to modify address) byte_tbl db 12,15,16,22,..... ; Table of bytes mov al,[byte_tbl+2] mov al,byte_tbl[2] ; same as the former Register Indirect (field points to a register that contains the operand address) mov ax,[di] The registers used for indirect addressing are BX, BP, SI, DI Base-index mov ax,[bx + di] For example, if we are talking about an array, BX contains the address of the beginning of the array, and DI contains the index into the array. Base-index with displacement mov ax,[bx + di + 10]