Freescale Semiconductor StarCore SC140 - Manual (Page 60)

2-28 SC140 DSP Core Reference Manual
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.
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
48 bits
D3.l D2.l D2.h D2.e
D0.h
D1.h D1.l
×
=
S Ext
+
D0.h
×
D1.l
D1.h
×
D0.h
Signed
× Unsigned
Signed
× Signed
D0,D1,D2
D2,D3)
D0,D1,D2
mpysu
(tfr
dmacss