Allen-Bradley Compact I/O 1769-ADN DeviceNet, Руководство пользователя

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1 Publication 1769-UM001B-EN-P - October 2002
Appendix
C
1769-ADN Throughput Characteristics
Read this appendix to learn about the 1769-ADN throughput
characteristics.
Series A Adapters
About Adapter
Throughput Characteristics
The following calculations provide a baseline for a 2-node network, a
scanner, and a 1769-ADN. These calculations do not incorporate the
impact of additional nodes on the network.
Specifically, nodes with addresses less than the node (1769-ADN)
being analyzed will produce higher priority (with respect to the
DeviceNet network) I/O messages and hence will lengthen any of the
times calculated.
Turn-Around Time (t
tat
) Turn-around time is defined as the time from when the 1769-ADN
receives an output update from the scanner to the time it produces the
entire input update that reflects the change provided in the output
update with a Change of State connection without acknowledgement.
Specifically, from the time the last output-update fragment is received
to the time that the last fragment
2
of the corresponding input-update is
sent. This includes:
•
time for the 1769-ADN to distribute the output update to all of
the output modules on the 1769 backplane/bus
•
the output module’s turn-on/off time
•
the input module’s filter time
•
time for the 1769-ADN to collect the (new) values from the input
modules
•
time for the 1769-ADN to transmit the complete input-update on
the network
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