ADDRESSING MODES

S3C84E5/C84E9/P84E9

 

 

INDIRECT ADDRESS MODE (IA)

In Indirect Address (IA) mode, the instruction specifies an address located in the lowest 256 bytes of the program memory. The selected pair of memory locations contains the actual address of the next instruction to be executed. Only the CALL instruction can use the Indirect Address mode.

Because the Indirect Address mode assumes that the operand is located in the lowest 256 bytes of program memory, only an 8-bit address is supplied in the instruction; the upper bytes of the destination address are assumed to be all zeros.

Current

Instruction

Sample Instruction:

Program Memory

dst

OPCODE

Lower Address Byte

Upper Address Byte

Next Instruction

LSB Must be Zero

Program Memory

Locations 0-255

CALL #40H

;The 16-bit value in program memory addresses 40H and 41H is the subroutine start address.

Figure 3-12. Indirect Addressing

3-12

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Samsung S3C84E5 user manual Indirect Address Mode IA, Call #40H