Freescale Semiconductor StarCore SC140 - Manual (Page 59)

DALU
SC140 DSP Core Reference Manual 2-27
Figure 2-8 illustrates the use of these instructions in the case of a double-precision multiplication of
32-bit x 32-bit operands. The “Unsigned x Unsigned” operation is used to multiply or multiply-accumulate
the unsigned low portion of one double-precision number with the unsigned low portion of the other
double-precision number. The “Signed x Unsigned” and “Unsigned x Signed” operations are used to
multiply or multiply-accumulate the signed high portion of one double-precision number with the unsigned
low portion of the other double-precision number. The “Signed x Signed” operation is used to multiply or
multiply-accumulate the two signed high portions of two signed double-precision numbers. The TFRx
instructions in parentheses are optional instructions that are used only in case all 64 bits of the result are
needed. Otherwise, the result is truncated to a 32-bit fraction.
Figure 2-8. Fractional Double-Precision Multiplication
32 bits
64 bits
D3.l D4.l D2.l D2.h D2.e
D0.l D0.h
D1.h D1.l
×
=
S Ext
+
+
+
D1.l
×
D0.l
D0.h
×
D1.l
D1.h
×
D0.l
D1.h
×
D0.h
Signed
× Unsigned
Signed
× Signed
Unsigned
× Unsigned
D0,D1,D2
D2,D3)
D0,D1,D2
D0,D1,D2
D2,D4)
D0,D1,D2
mpyuu
(tfr
dmacsu
macus
(tfr
dmacss
Unsigned
× Signed