Freescale Semiconductor SC140 specifications Integer Multi-Precision Arithmetic

Models: SC140

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DALU

Figure 2-9 illustrates the use of the fractional multiplication and multiply-accumulate instructions in the case of a mixed double-precision multiplication of 16-bit by 32-bit signed operands. The “Signed x Unsigned” operation is used to multiply the signed high portion of one single-precision number with the unsigned low portion of the other double-precision number. The “Signed x Signed” DMAC operation is used to multiply-accumulate the two signed high portions of the two signed operands. The TFRx instruction in parentheses is an optional instruction that is used only in case all 48 bits of the result are needed. Otherwise, the result is truncated to a 32 bit fraction.

D0.h

D1.h

D1.l

mpysu D0,D1,D2

(tfr D2,D3)

=

Signed Unsigned

D0.h D1.l

Signed Signed

dmacss D0,D1,D2

S Ext

D1.h D0.h

+

D2.e

D2.h

D2.l

D3.l

48 bits

Figure 2-9. Fractional Mixed-Precision Multiplication

2.2.2.8.2 Integer Multi-Precision Arithmetic

A set of DALU operations is provided for integer multi-precision multiplications. When these instructions are used, the multiplier accepts some combinations of two’s complement signed and unsigned formats. Both signed and unsigned multi-precision multiplication are supported. Table 2-16 lists these instructions.

Table 2-16. Integer Signed and Unsigned Two’s Complement Multiplication

Instruction

Description

 

 

 

 

IMPYSU/IMACSU

Integer multiplication and multiply-accumulate with signed x unsigned operands

 

 

IMPYUU

Integer multiplication with unsigned x unsigned operands

 

 

IMPYHLUU

Integer multiply unsigned x unsigned:

 

first source from high portion, second from low portion

 

 

IMACLHUU

Integer multiply-accumulate unsigned x unsigned:

 

first source from low portion, second from high portion

 

 

2-28

SC140 DSP Core Reference Manual

Page 60
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Freescale Semiconductor SC140 specifications Integer Multi-Precision Arithmetic, Fractional Mixed-Precision Multiplication