Indirect Register Addressing Mode (Ir) - Samsung S3C80A5B User Manual

S3C80A5B

INDIRECT REGISTER ADDRESSING MODE (IR)

In Indirect Register (IR) addressing mode, the content of the specified register or register pair is the address of the
operand. Depending on the instruction used, the actual address may point to a register in the register file, to program
memory (ROM), or to an external memory space, if implemented (see Figures 3-3 through 3-6).
You can use any 8-bit register to indirectly address another register. Any 16-bit register pair can be used to indirectly
address another memory location. Remember, however, that locations C0H–FFH in set 1 cannot be accessed using
Indirect Register addressing mode.
8-bit Register
File Address
One-Operand
Instruction
(Example)
Sample Instruction:
RL
Program Memory
dst
OPCODE
Instruction Execution
@SHIFT ; Where SHIFT is the label of an 8-bit register address.
Figure 3-3. Indirect Register Addressing to Register File
Point to One
Register in
Register File
Address of Operand
used by Instruction
Value used in
ADDRESSING MODES
Register File
ADDRESS
OPERAND
3-3