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<h2>
  <a name="1102447"> </a><font color="#003366"  face="Verdana, Arial, Helvetica, sans-serif">5.7 	 Scaling</font>
</h2><hr>


<p>
  <a name="1102448"> </a><font size=2  face="Verdana, Arial, Helvetica, sans-serif">The <strong>biquad</strong> and <strong>smacloop</strong> operations are performed with an oversize accumulator of 48 bits. The accumulator value is always sign-extended to the full width of the accumulator.</font>
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<p>
  <a name="1102449"> </a><font size=2  face="Verdana, Arial, Helvetica, sans-serif">During a multiply-accumulate sequence the value in the accumulator may temporarily go outside the representable range of the final result, but can never overflow the accumulator for a single <strong>biquad</strong> or <strong>smacloop</strong>.</font>
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<h3>
  <a name="1102450"> </a><font color="#003366"  face="Verdana, Arial, Helvetica, sans-serif">5.7.1 	 Accumulator scaling</font>
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<p>
  <a name="1102451"> </a><font size=2  face="Verdana, Arial, Helvetica, sans-serif">The user-visible accumulator is either in <em>LongMode</em> (<span class=Signal>Q31</span>) or <em>ShortMode</em> (<span class=Signal>Q15</span>). For <strong>smacloop</strong>, the mode is defined by the <span class=Signal>mac_mode</span> <span class=Signal>Status</span> register field. <strong>biquad</strong> only supports <em>ShortMode</em>.</font>
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<p>
  <a name="1102452"> </a><font size=2  face="Verdana, Arial, Helvetica, sans-serif">Pre-scaling converts the user-visible accumulator to an internal format accumulator, as shown in <a href="multacc8.htm#1105732"><font  color="#0000ff" face="Verdana, Arial, Helvetica, sans-serif"><i>Figure

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