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8
After moving the cursor to the
Attn
field, press the CHANGE and ENTER keys
on the Send PLCA-22 analyzer to increment the
Attn
level by 6dB. Then clear
the status on the UUT by responding with a "Y" to the Nodeutil prompt and then
press START on the Send PLCA-22 analyzer.
9
Repeat steps 7 through 8 above for all
Send
Attn
levels up to, and including
24dB, recording the results each time in table 7.1.
10
To test the UUT's secondary operating frequency, change the PLCA-22 analyzers
from
UnackPri
to
UnackSec
mode. Repeat steps 6 through 9, above, but record
the results in table 7.2.
Notes:
The calculation of packet error rate used in the above verification procedure avoids inaccuracies
which would result from the use of CRC error count to compute packet error rate. It does, however,
make use of one simplifying approximation which does not alter the resultant observed sensitivity.
The material in this note is provided for other applications where a precise measure of packet error
rate may be required.
Packet error rate actually includes both packets received with an incorrect CRC plus any packets
which were so weak or corrupted they were not detected at all. These “missed packets” are, by
definition, not included in the CRC error count of a node. For a physical layer packet error rate of
10%, the percentage of missed packets is generally negligible. Under conditions where the packet
error rate is greater than 10%, a significant portion of the error rate may be due to missed packets.
The “Packets received by node" field in Nodeutil software yields the actual number of packets
correctly received by the node. Subtracting this number from the total number of packets sent gives
the exact packet error count, including missed packets.
In addition to the number of test packets selected on the PLCA-22 analyzers, the total number of
packets sent on the power line actually includes several control packets sent between the PLCA-22
analyzers. These control packets are used by the PLCA-22 analyzers to synchronize their settings
before the test, and to exchange data related to the test immediately after the test. Additionally,
querying the status of the UUT causes some packets to be logged, the number of which will depend
on the tool used and the firmware version number of the UUT’s Neuron Chip. This number can be
determined by performing a non-attenuated, noise-free test with the PLCA-22 analyers and then
observing the number of “Packets received by node” above the number of test packets defined on the
PLCA-22 analyzer. The total overhead is generally either 11 or 13 packets.
Given the above, a more accurate formula for calculating the physical layer packet error rate with
1000 test packets is then:
PER% = (1011 - # “Packets received by node”) x 100 / 1011
L
ON
W
ORKS
PLT-22 Transceiver User’s Guide
7-15
Содержание LONWORKS PLT-22
Страница 6: ...iv Echelon...
Страница 14: ...1 8 Introduction...
Страница 67: ...LONWORKS PLT 22 Transceiver s User Guide 5 7 Figure 5 3 Capacitor Input Power Supply Schematic...
Страница 92: ...6 10 Design and Test for Electromagnetic Compatibility...
Страница 110: ...7 18 Communication Performance Verification...
Страница 114: ...8 4 References...
Страница 118: ...A 4 Appendix A...