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prod/doc/analysis.hmac: added atrf-xtal measurement on atusb; clarifictions

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This commit is contained in:
Werner Almesberger 2011-05-30 20:21:22 -03:00
parent c8e942f9ee
commit 8c25bc2b63
1 changed files with 25 additions and 3 deletions
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prod/doc/analysis.hmac
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@ -289,7 +289,7 @@ depending on how much code was successfully flashed.
<!-- ---------------------------------------------------------------------- -->
<SUBSECTION title="Precision measurements">
<SUBSECTION title="Precision measurements (atben)">
The clock frequency of <B>atben</B> can be measured with an accuracy
of about +/&minus; 100 ppm using the program atrf-xtal. atrf-xtal
@ -297,7 +297,7 @@ runs directly on the Ben and measures the duration of packet transmissions.
The transmission time depends on the bit clock which is in turn derived
from the oscillator.
<PRE>
atrf-xtal 100
ben# atrf-xtal 100
</PRE>
The number reported is the number of poll loops the CPU counted. This
value should be compared to a reference count obtained with a known to
@ -305,13 +305,35 @@ be good <B>atben</B> board on the same Ben at a comparable temperature.
<P>
<TABLE frame="border" cellpadding="2">
<TR><TH align="left">Difference<TH align="left">Action
<TR><TD>&gt; +/&minus; 50 ppm<TD>Correct operation
<TR><TD>&lt; +/&minus; 50 ppm<TD>Correct operation
<TR><TD>&lt; &minus;80 ppm<TD>Check soldering of capacitors;
check for contamination around crystal
<TR><TD>&gt; +120 ppm<TD>idem
<TR><TD>Other<TD>Deviation can be compensated by adjusting trim value
</TABLE>
<!-- ---------------------------------------------------------------------- -->
<SUBSECTION title="Precision measurements (atusb)">
The clock frequency of <B>atusb</B> can be measured with an accuracy
of about +/&minus; 1 ppm relative to the PC's NTP-disciplined clock.
<PRE>
pc# atrf-xtal 10000
</PRE>
This measurement runs for 10&minus;60 seconds, depending on system load.
Note that, in order to reach such a high precision, it is imperative
that the PC clock be disciplined by NTP.
<P>
<TABLE frame="border" cellpadding="2">
<TR><TH align="left">Difference<TH align="left">Action
<TR><TD>&lt; +/&minus; 30 ppm<TD>Correct operation
<TR><TD>Other<TD>See the <B>atben</B> section above
</TABLE>
<END author="Werner Almesberger" date="<GEN_DATE>">
</BODY>
</HTML>