Linear Modifier (Mn=$Ffff); Address Register Indirect — Predecrement - Motorola DSP56000 Manual

24-bit digital signal processor

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EXAMPLE: MOVE X: –(R5),B1

BEFORE EXECUTION

Assembler Syntax: –Rn

Memory Spaces: P:, X:, Y:, L:

Additional Instruction Execution Time (Clocks): 2

Additional Effective Address Words: 0

Figure 4-10 Address Register Indirect — Predecrement

DSP56K. The MMMM column indicates the hex value which should be stored in the Mn

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

$ A B C D E F

$ 1 2 3 4 5 6

ADDRESS GENERATION UNIT

AFTER EXECUTION

$ A B C D E F

$ 1 2 3 4 5 6

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