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

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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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@ -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 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 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 The transmission time depends on the bit clock which is in turn derived
from the oscillator. from the oscillator.
<PRE> <PRE>
atrf-xtal 100 ben# atrf-xtal 100
</PRE> </PRE>
The number reported is the number of poll loops the CPU counted. This 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 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> <P>
<TABLE frame="border" cellpadding="2"> <TABLE frame="border" cellpadding="2">
<TR><TH align="left">Difference<TH align="left">Action <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; <TR><TD>&lt; &minus;80 ppm<TD>Check soldering of capacitors;
check for contamination around crystal check for contamination around crystal
<TR><TD>&gt; +120 ppm<TD>idem <TR><TD>&gt; +120 ppm<TD>idem
<TR><TD>Other<TD>Deviation can be compensated by adjusting trim value <TR><TD>Other<TD>Deviation can be compensated by adjusting trim value
</TABLE> </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>"> <END author="Werner Almesberger" date="<GEN_DATE>">
</BODY> </BODY>
</HTML> </HTML>