Freescale Semiconductor SC140 specifications Viterbi Decoding Support

Models: SC140

1 760
Download 760 pages 48.94 Kb
Page 62
Image 62

DALU

Figure 2-11 illustrates the use of these instructions in the case of an unsigned integer double-precision multiplication of 32-bit by 32-bit unsigned operands. In this example, only a 32-bit result is generated. The most significant 32-bits are shifted out. All multiplications are of the “Unsigned x Unsigned” type using different combinations of high and low portions.

impyuu d0,d1,d2

impyhluu d0,d1,d3 imaclhuu d0,d1,d3

aslw d3

add d2,d3

D0.h

 

D0.l

 

 

 

 

D1.h

 

D1.l

 

 

 

=

Unsigned Unsigned

D1.l D0.l

Unsigned Unsigned

D0.h D1.l

+

D1.h D0.l

+

 

 

D3.l

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D3.h

 

 

D3.l

 

 

 

 

 

 

 

 

 

 

 

 

32 bits

 

 

 

 

 

 

 

Figure 2-11. Unsigned Integer Double-Precision Multiplication

2.2.2.9 Viterbi Decoding Support

A set of DALU and AGU operations is provided for Viterbi decoding kernels. A special MAX2VIT operation is defined. This instruction functions as a regular MAX2 instruction and is used to transfer two 16-bit maximum signed values. In addition, the MAX2VIT instruction updates two Viterbi flags (VFs) which reside in the status register as described in Section 3.1.1, “Status Register (SR),” on page 3-1. Complementary AGU move operations are provided (VSL instructions). For a full description of the Viterbi instructions, see Appendix A, “Viterbi Shift Left Move (AGU) VSL,” on page A-422.

2-30

SC140 DSP Core Reference Manual

Page 62
Image 62
Freescale Semiconductor SC140 specifications Viterbi Decoding Support, Unsigned Integer Double-Precision Multiplication