dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 179

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

The following sections demonstrate the use of these instructions in multi-precision integer multiplications.
5.5.3.1
Figure 5-22 and Example 5-23 demonstrate a signed multiplication of two 32-bit long values that generates
a 32-bit long integer result.
C1:C0 = A1:A0 × B1:B0
(Both 32-Bit Operands Are Signed)
;Signed x Signed 32-Bit Integer Multiplication
This example, which saves only the lower 32 bits of the result, does not require the A1 × B1 product,
which only affects the upper 32 bits of the result. Also note that C2 in the final result is modified and does
not contain valid data.
Freescale Semiconductor
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IMPYSU—multiplication with one signed and one unsigned operand
(signed 16-bit operand located in FF1 portion, unsigned in FF0)
IMPYUU—multiplication with two unsigned operands (2 cases)
(each unsigned 16-bit operand located in the FF0 portion)
(first 16-bit operand located in FF1 portion, second in FF0)
IMPYSU
IMACUS
IMPYUU
ADD
Signed 32-Bit × Signed 32-Bit with 32-Bit Result
Figure 5-22. 32-Bit × 32-Bit –> 32-Bit Signed Integer Multiplication
Example 5-23. Multiplying Two Signed Long Integers
A1,B0,Y
A0,B1,Y
A0,B0,C
Y0,C
Data Arithmetic Logic Unit
; Y1:Y0 = signed A1 x unsigned B0
; Y1:Y0 = unsigned A0 x signed B1 + Y1:Y0
; C2:C1:C0 = unsigned A0 x unsigned B0
; Combine Results: final 32-bit result in C
Signed × Unsigned
Unsigned × Signed
×
+
C2
A1 × B0
A0 × B1
Extended- and Multi-Precision Operations
Unsigned × Unsigned
A1
B1
C1
A0 × B0
32 Bits
32 Bits
32 Bits
C0
A0
B0
5-33