Texas Instruments TMS320C3x - Manual (Page 167)

Indirect Addressing
6-14
Example 6–13. Indirect Addressing With Preindex Add and Modify
The address of the operand to fetch is the sum of an auxiliary register (AR n) and
an index register (IR0 or IR1). After the data is fetched, the auxiliary register is
updated with the generated address.
Operation: operand address = AR n + IRm
AR n = ARn + IRm
Assembler Syntax: *++ AR n(IRm)
Modification Field: 01010 if m = 0
10010 if m = 1
(+)
0
0 31 24 23
Address x x AR n
31
IR m x
0
31
Index
Operand
24 23
x
Example 6–14. Indirect Addressing With Preindex Subtract and Modify
The address of the operand to fetch is the difference between an auxiliary register
(AR
n) and an index register (IR0 or IR1). The resulting address becomes the new
contents of the auxiliary register.
Operation: operand address = AR n – IRm
AR n = ARn – IRm
Assembler Syntax: *– – AR n(IRm)
Modification Field: 01011 if m = 0
10011 if m = 1
(–)
0
0 31 24 23
Address x x AR n
31
IR m x
0
31
Index
Operand
24 23
x