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prod/doc/analysis.html: added borders to tables; use −

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Werner Almesberger 2011-05-19 14:46:53 -03:00
parent 926ed26188
commit f52fbe1f6f
1 changed files with 11 additions and 11 deletions
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prod/doc/analysis.html
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@ -29,7 +29,7 @@ Voltages should be tested in the following order: USB, then I/O, then
digital, and finally analog. The table below gives the permissible
ranges. Any voltages outside of these ranges indicate a problem.
<P>
<TABLE>
<TABLE frame="border" cellpadding="2">
<TR><TH>Domain<TH>Nominal<TH>Minimum<TH>Maximum
<TR><TD>USB<TD>5.0 V<TD>4.5 V<TD>5.25 V
<TR><TD>I/O<TD>3.3 V<TD>3.0 V<TD>3.6 V
@ -90,12 +90,12 @@ operation. Anomalies are easy to detect with even a low-cost oscilloscope
and pinpoint specific problems and help to select further analysis steps.
<P>
The crystal used in <B>atben</B> and <B>atusb</B> has a nominal tolerance
of +/- 15 ppm at 22-28 C. Low-cost oscilloscopes typically have a timing
of +/&minus; 15 ppm at 22-28 C. Low-cost oscilloscopes typically have a timing
accuracy of
+/- 100 ppm, which means that only major excursions can be detected by
+/&minus; 100 ppm, which means that only major excursions can be detected by
measuring the clock output with such an instrument. Full-speed USB only
requires an accuracy of +/- 2500 ppm.
We can therefore consider all results within a range of +/- 1000 ppm as
requires an accuracy of +/&minus; 2500 ppm.
We can therefore consider all results within a range of +/&minus; 1000 ppm as
sufficient, and perform more precise measurements by other means. This
applies to <B>atben</B> as well as to <B>atusb</B>.
<P>
@ -114,7 +114,7 @@ atrf-txrx -d net:ben -C 1
This configures <B>atben</B> as a promiscuous receiver. The reception
of any IEEE 802.15.4 frame or pressing Ctrl-C will terminate the command.
<P>
<TABLE>
<TABLE frame="border" cellpadding="2">
<TR><TH align="left">Clock<TH align="left">Action
<TR><TD>0 Hz<TD>Check voltages; check that the clock is enabled;
check for shorts around crystal; check connectivity of crystal
@ -136,7 +136,7 @@ the transceiver generates a 1 MHz clock. When the microcontrolled comes out
of reset, it raises the transceiver's clock output to 8 MHz and then
enables USB.
<P>
<TABLE>
<TABLE frame="border" cellpadding="2">
<TR><TH align="left">Clock<TH align="left">Action
<TR><TD>0 Hz<TD>Check voltages; check for shorts around crystal; check
connectivity of crystal
@ -154,7 +154,7 @@ enables USB.
<H3>Precision measurements</H3>
The clock frequency of <B>atben</B> can be measured with an accuracy
of about +/- 100 ppm using the program <B>atrf-xtal</B>. <B>atrf-xtal</B>
of about +/&minus; 100 ppm using the program <B>atrf-xtal</B>. <B>atrf-xtal</B>
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.
@ -169,10 +169,10 @@ 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
be good <B>atben</B> board and the same Ben at a comparable temperature.
<P>
<TABLE>
<TABLE frame="border" cellpadding="2">
<TR><TH align="left">Difference<TH align="left">Action
<TR><TD>&gt; +/- 50 ppm<TD>Correct operation
<TR><TD>&lt; -80 ppm<TD>Check soldering of capacitors;
<TR><TD>&gt; +/&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>Divergence can be compensated by adjusting trim value