User`s manual

Data Operations

Using the barrel shifter

MOTOROLA Optimizing DSP56300/DSP56600 Applications 2-9

will normalize A, so that in the DSP56300 it’s leading one or zero

will be shifted to Bit 46 in the accumulator. If |A| > 1 (meaning that

it spilled to the extension A2), then CLB returns a positive number

(between 1 and 8). If |A| < 1, CLB returns a zero or a negative

number (between –47 and 0). The two cases in Figure 2-1 exemplify

the normalization operation for the DSP56300. The NORMF at the

56600 core operates similarly, with adjustments to the different

accumulator length.

The NORMF instruction can be used to keep data dynamically

bounded (maximizing calculation accuracy), implement floating

point routines, normalizing data blocks, and more. For example,

consider the following routine for efficiently normalizing a data

block. The first pass finds the normalization factor (using MAXM

and CLB) and the second pass performed the normalization itself.

;NORMALIZING A DATA BLOCK

;=========================

;X:base - base address of un-normalized data.

;Y:base - base address of normalized data.

;N: data block size

;cycle count

move #base,r0 ; 1

move #base,r1 ; 1

clr b x:(r0)+,a ; 1 + 2 pointer interlock

rep #N ; 5

maxm a,b x:(r0)+,a ; 1 x N

move r1,r0 ; 1

clb b,a ; 1

Figure 2-1 The Fast Normalization Operation for the DSP56300:

0234755

0c 020000 100000

00 000005 000000

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A 00 601000 008000

CLB

NORMF

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00 00c000 003000

ff fffff9 000000

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A 00 600000 180000

A,B

B1,A

AA0831