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ADDRESSING MODES
REGISTER ADDRESSING MODE (R)
In Register addressing mode (R), the operand value is the content of a specified register or register pair
(see Figure 3-1).
Working register addressing differs from Register addressing in that 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
Sample Instruction:
DEC
4-bit
Working Register
Two-Operand
Instruction
(Example)
Sample Instruction:
ADD
3-2
Program Memory
OPCODE
Instruction
(Example)
CNTR
Figure 3-1. Register Addressing
Program Memory
dst
src
OPCODE
R1, R2
Figure 3-2. Working Register Addressing
S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
dst
Point to One
Register in Register
File
Instruction Execution
;
Where CNTR is the label of an 8-bit register address
MSB Point to
RP0 ot RP1
3 LSBs
Point to the
Working Register
(1 of 8)
;
Where R1 and R2 are registers in the currently
selected working register area.
Register File
OPERAND
Value used in
Register File
RP0 or RP1
OPERAND
Selected
RP points
to start
of working
register
block
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