ADDRESSING MODES
S3C80A5B
3-2
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).
dst
Value used in
Instruction Execution
OPCODE
OPERAND
8-bit Register
File Address
Point to One
Register in Register
File
One-Operand
Instruction
(Example)
Sample Instruction:
DEC
CNTR
; Where CNTR is the label of an 8-bit register address
Register File
Program Memory
Figure 3-1. Register Addressing
4-bit
Working Register
Points to the
Working Register
(1 of 8)
Two-Operand
Instruction
(Example)
Sample Instruction:
ADD
R1, R2 ; Where R1 and R2 are registers in the currently
selected working register area.
Program Memory
Register File
3 LSBs
RP0 or RP1
Selected
RP Points
to Start
of Working
Register
Block
MSB Points to
RP0 ot RP1
dst
OPCODE
src
OPERAND
Figure 3-2. Working Register Addressing