dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 44

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

and rounds down any value below one-half. The question arises as to which way one-
half should be rounded. If it is always rounded one way, the results will eventually be
biased in that direction. Convergent rounding solves the problem by rounding down if the
number is odd (LSB=0) and rounding up if the number is even (LSB=1). Figure 3-10
shows the four cases for rounding a number in the A1 (or B1) register. If scaling is set in
the status register, the resulting number will be rounded as it is put on the data bus. How-
ever, the contents of the register are not scaled.
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S
S
S
MSP
SIGNED MULTIPLIER
SIGN EXTENSION
2N — 1 PRODUCT
INTEGER
Figure 3-9 Integer/Fractional Multiplication Comparison
2N BITS
DATA REPRESENTATION AND ROUNDING
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.
Freescale Semiconductor, Inc.
S
For More Information On This Product,
SIGNED MULTIPLICATION N x N - 2N – 1 BITS
DATA ARITHMETIC LOGIC UNIT
LSP
Go to: www.freescale.com
•
S
S•
MSP
SIGNED MULTIPLIER
2N — 1 PRODUCT
FRACTIONAL
. .
.
2N BITS
S
LSP
ZERO FILL
MOTOROLA
0