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ADDRESSING MODES
REGISTER ADDRESSING MODE (R)
In Register addressing mode, the operand is the content of a specified register (see Figure 3-1). Working register
addressing differs from Register addressing because it uses an 16-byte working register space in the register file
and an 4-bit register within that space (see Figure 3-2).
8-Bit Register
File Address
One-Operand
Instruction
(Example)
Sample Instruction:
DEC
CNTR
4-Bit
Working Register
Two-Operand
Instruction
(Example)
Sample Instruction:
ADD
3-2
Program Memory
dst
OPCODE
;
Where CNTR is the label of an 8-bit register address
Figure 3-1. Register Addressing
Program Memory
dst
src
OPCODE
R1, R2
;
Where R1 and R2 are registers in the currently selected
working register area.
Figure 3-2. Working Register Addressing
Point to one
register in register
file
Value used in
Instruction Execution
Register File
MSB point to
RP0 to RP1
RP0 or RP1
3 LSBs
Point to the
working register
(1 of 8)
Register File
OPERAND
Selected
RP points to
start of
working
register block
OPERAND
S3C9454B/F9454B
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