Texas Instruments TMS320C3x - Manual (Page 157)

Direct Addressing
6-4
6.3 Direct Addressing
In direct addressing, the data address is formed by the concatenation of the
eight LSBs of the data-page pointer (DP) with the 16 LSBs of the instruction
word (expr). This results in 256 pages (64K words per page), allowing you to
access a large address space without requiring a change of the page pointer.
The syntax and operation for direct addressing are:
Syntax: @expr
Operation: address = DP concatenated with expr
Figure 6–1 shows the formation of the data address. Example 6–1 is an instruc-
tion example with data before and after instruction execution.
Figure 6–1. Direct Addressing
0
0 31 16 15
0 0
0
31
address
operand
page
expr
x x . . . x x
0 . . . 0
31 8 7 0
24 23 31
DP
Instruction
word
(Data-
page pointer)
Example 6–1. Direct Addressing
ADDI @0BCDEh,R7
Before Instruction After Instruction
R7 00 0000 0000 R7 00 1234 5678
DP 8A DP 8A
Data memory
8ABCDEh 1234 5678 8ABCDEh 1234 5678