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S3C84E5/C84E9/P84E9 ADDRESSING MODES
3-13
RELATIVE ADDRESS MODE (RA)
In Relative Address (RA) mode, a twos-complement signed displacement between – 128 and + 127 is specified in
the instruction. The displacement value is then added to the current PC value. The result is the address of the next
instruction to be executed. Before this addition occurs, the PC contains the address of the instruction immediately
following the current instruction.
Several program control instructions use the Relative Address mode to perform conditional jumps. The instructions
that support RA addressing are BTJRF, BTJRT, DJNZ, CPIJE, CPIJNE, and JR.
OPCODE
Program Memory
Displacement
Program Memory
Address Used
Sample Instructions:
JR ULT,$+OFFSET ; Where OFFSET is a value in the range +127 to -128
Next OPCODE
+
Signed
Displacement Value
Current Instruction
Current
PC Value
Figure 3-13. Relative Addressing