ADDRESSING
4 - 16 ADDRESS GENERATION UNIT
MOTOROLA
DSP56K. The MMMM column indicates the hex value which should be stored in the Mn
register.
4.4.2.1 Linear Modifier (Mn=$FFFF)
When the value in the modifier register is $FFFF, address modification is performed using
normal 16-bit linear arithmetic (see Table 4-2). A 16-bit offset, Nn, and + 1 or –1 can be
used in the address calculations. The range of values can be considered as signed (Nn
from –32,768 to + 32,767) or unsigned (Nn from 0 to + 65,535) since there is no arithmetic
15 0
15 0
15 0
EXAMPLE: MOVE X: –(R5),B1
BEFORE EXECUTION AFTER EXECUTION
B2 B1 B0
55 48 47 24 23 0
7 0 23 0 23 0
X MEMORY
23 0
$3006
$3007
$FFFF
R5
N5
M5
Assembler Syntax: –Rn
Memory Spaces: P:, X:, Y:, L:
Additional Instruction Execution Time (Clocks): 2
Additional Effective Address Words: 0
$3007
3B123 45 6A554C 0
B2 B1 B0
55 48 47 24 23 0
7 0 23 0 23 0
XXXX
15 0
15 0
15 0
X MEMORY
23 0
$3006
$3006
$FFFF
R5
N5
M5
$3007 $ABCDEF
XXXX
$123456
$ABCDEF
$123456
3BB62D04A554C0
Figure 4-10 Address Register Indirect — Predecrement