2.3.2.248-Bit25.23NumberFormat
2
−23
Bit
S_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx.xxxx_xxxx_xxxx_xxxx_xxxx_xxx
2
0
Bit
2
16
Bit
2
22
Bit
Sign Bit
2
23
Bit
2
−1
Bit
2
−10
Bit
M0007-02
(1 or 0) y 2
23
+ (1 or 0) y 2
22
+ … + (1 or 0) y 2
0
+ (1 or 0) y 2
−1
+ … + (1 or 0) y 2
−23
2
23
Bit 2
22
Bit 2
0
Bit 2
−1
Bit 2
−23
Bit
M0008-02
TAS5518C
8-ChannelDigitalAudioPWMProcessor
www.ti.com
SLES238A–SEPTEMBER2008–REVISEDJULY2009
concatenatedwiththehexvalueofthefractionalpartofthegaincoefficienttoformthe32-bitI
2
C
coefficient.Thereasonisthatthe28-bitcoefficientcontains5bitsofinteger,andthustheintegerpartof
thecoefficientoccupiesallofonehexdigitandthemostsignificantbitofthesecondhexdigit.Inthesame
way,thefractionalpartoccupiesthelowerthreebitsofthesecondhexdigit,andthenoccupiestheother
fivehexdigits(withtheeighthdigitbeingthezero-valuedmostsignificanthexdigit).
Allleveladjustmentandthresholdcoefficientsare48-bitcoefficientsusinga25.23numberformat.
Numbersformattedas25.23numbershave25bitstotheleftofthedecimalpointand23bitstotheright
ofthedecimalpoint.ThisisshowninFigure2-7.
Figure2-7.25.23Format
Figure2-8showsthederivationofthedecimalvalueofa48-bit25.23formatnumber.
Figure2-8.ConversionWeightingFactors—25.23FormattoFloatingPoint
Two32-bitwordsmustbesentovertheI
2
Cbustodownloadalevelorthresholdcoefficientintothe
TAS5518C.Thealignmentofthe48-bit,25.23formattedcoefficientinthe8-byte(two32-bitwords)I
2
C
wordisshowninFigure2-9.
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