Computer Hardware User's Guide

Indirect Addressing
6-17 Addressing Modes
Example 6–19. Indirect Addressing With Postindex Add and Bit-Reversed Modify
The address of the operand to fetch is the contents of an auxiliary register
(AR n ). After the operand is fetched, the index register (IR0) is added to the
auxiliary register. This addition is performed with a reverse-carry propagation
and can be used to yield a bit-reversed (B) address. This value replaces the
contents of the auxiliary register.
Operation: operand address = AR
n
AR n = B(AR n + IR0)
Assembler Syntax: *AR n ++(IR0)B
Modification Field: 11001
(+)
0
0
31 24 23
Addressxx
AR n
31
xx
0
31
24 23
Index
Operand
(B)
IR m