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prod/doc/analysis.hmac: added atrf-xtal measurement on atusb; clarifictions
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@ -289,7 +289,7 @@ depending on how much code was successfully flashed.
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<!-- ---------------------------------------------------------------------- -->
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<SUBSECTION title="Precision measurements">
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<SUBSECTION title="Precision measurements (atben)">
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The clock frequency of <B>atben</B> can be measured with an accuracy
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of about +/− 100 ppm using the program atrf-xtal. atrf-xtal
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@ -297,7 +297,7 @@ runs directly on the Ben and measures the duration of packet transmissions.
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The transmission time depends on the bit clock which is in turn derived
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from the oscillator.
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<PRE>
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atrf-xtal 100
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ben# atrf-xtal 100
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</PRE>
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The number reported is the number of poll loops the CPU counted. This
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value should be compared to a reference count obtained with a known to
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@ -305,13 +305,35 @@ be good <B>atben</B> board on the same Ben at a comparable temperature.
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<P>
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<TABLE frame="border" cellpadding="2">
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<TR><TH align="left">Difference<TH align="left">Action
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<TR><TD>> +/− 50 ppm<TD>Correct operation
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<TR><TD>< +/− 50 ppm<TD>Correct operation
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<TR><TD>< −80 ppm<TD>Check soldering of capacitors;
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check for contamination around crystal
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<TR><TD>> +120 ppm<TD>idem
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<TR><TD>Other<TD>Deviation can be compensated by adjusting trim value
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</TABLE>
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<!-- ---------------------------------------------------------------------- -->
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<SUBSECTION title="Precision measurements (atusb)">
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The clock frequency of <B>atusb</B> can be measured with an accuracy
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of about +/− 1 ppm relative to the PC's NTP-disciplined clock.
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<PRE>
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pc# atrf-xtal 10000
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</PRE>
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This measurement runs for 10−60 seconds, depending on system load.
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Note that, in order to reach such a high precision, it is imperative
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that the PC clock be disciplined by NTP.
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<P>
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<TABLE frame="border" cellpadding="2">
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<TR><TH align="left">Difference<TH align="left">Action
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<TR><TD>< +/− 30 ppm<TD>Correct operation
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<TR><TD>Other<TD>See the <B>atben</B> section above
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</TABLE>
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<END author="Werner Almesberger" date="<GEN_DATE>">
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</BODY>
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</HTML>
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