Zilog Z8F0130 - Manual (Page 58)

eZ8
™
CPU Core
User Manual
UM012820-0810 Addressing Modes
36
Relative Addressing
Figure 15 displays the Relative Addressing mode, symbol RA. The
instruction specifies a two’s complement signed displacement in the range
of –128 to +127. This instruction, added to the contents of the Program
Counter, obtains the address of the next instruction to be executed. Prior
to the addition operation, the Program Counter contains the address of the
instruction immediately following the current relative addressing instruc-
tion. The JR and DJNZ instructions are the only instructions that use this
mode.
Figure 15. Relative Addressing
8-bit Value
Program Memory
–128 to +127
One Operand
Instruction
(Example) Op Code
Displacement
Next Op Code
Next Op Code
if Jump
16-bit Program
Memory address
is PC[15:0] + d[7:0]
if no Jump
+
PC[15:0]
d If Jump taken,
PC[15:0] = PC[15:0] + d[7:0]
16-bit Program
Memory address
is PC[15:0]