Indirect Addressing
6-9
Addressing Modes
Example 6–3. Indirect Addressing With Predisplacement Add
The address of the operand to fetch is the sum of an auxiliary register (AR
n) and
the displacement (
disp). The displacement is either an 8-bit unsigned integer
contained in the instruction word or an implied value of 1.
Operation:
operand address = AR
n + disp
Assembler Syntax:
*+AR
n(disp)
Modification Field:
00000
(+)
0
0
31
24 23
Address
x
AR
n
31
disp
0
0
0
31
8
7
Integer
Operand
0...0
x
Example 6–4. Indirect Addressing With Predisplacement Subtract
The address of the operand to fetch is the contents of an auxiliary register
(AR
n) minus the displacement (disp). The displacement is either an 8-bit
unsigned integer contained in the instruction word or an implied value of 1.
Operation:
operand address = AR
n – disp
Assembler Syntax:
*–AR
n(disp)
Modification Field:
00001
(–)
0
0
31
24 23
Address
x
x
AR
n
31
disp
0
0
0
31
8
7
Integer
Operand
0...0