S3F84B8_UM_REV 1.00 3 ADDRESSING MODES
3-2
3.2 REGISTER (R) ADDRESSING MODE
In Register (R) addressing mode, the operand value is the content of a specified register or register pair (see
Figure 3-1
).
Working register addressing differs from Register addressing since 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
Program Memory Register File
Figure 3-1 Register Addressing
dst
OPCODE
4-bit
Working Register
Point 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
src
3 LSBs
RP0 or RP1
Selected
RP points
to start
of working
register
block
OPERAND
MSB Point to
RP0 ot RP1
Figure 3-2 Working Register Addressing
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