Register Addressing Mode (R) - Samsung S3C80A5B User Manual

ADDRESSING MODES

REGISTER ADDRESSING MODE (R)

In Register addressing mode, the operand is the content of a specified register or register pair (see Figure 3-1).
Working register addressing differs from Register addressing because it uses a register pointer to specify an 8-byte
working register space in the register file and an 8-bit register within that space (see Figure 3-2).
8-bit Register
File Address
One-Operand
Instruction
(Example)
Sample Instruction:
DEC
4-bit
Working Register
Two-Operand
Instruction
(Example)
3-2
Program Memory
dst
OPCODE
CNTR ; Where CNTR is the label of an 8-bit register address
Figure 3-1. Register Addressing
Program Memory
dst src
OPCODE
Sample Instruction:
ADD R1, R2 ;
Figure 3-2. Working Register Addressing
Point to One
Register in Register
File
Value used in
Instruction Execution
MSB Points to
RP0 ot RP1
3 LSBs
Points to the
Working Register
(1 of 8)
Where R1 and R2 are registers in the currently
selected working register area.
Register File
OPERAND
Register File
RP0 or RP1
OPERAND
S3C80A5B
Selected
RP Points
to Start
of Working
Register
Block