Functioning Of Switches; Store-And-Forward Switching Mode; Line Depth In Profinet; Port Speed & Duplex Mode - WAGO 852-112/000-001 Manual

852-112/000-001

3.5 Functioning of Switches

Switches analyze all incoming data packages and forward them to the port where the cor-
responding destination address is located. Exceptions are the multicast and broadcast
telegrams, which are forwarded to all active ports of the switch.
For selective forwarding of the telegrams, each switch contains of an address / port as-
signment table in which the assignments of the destination addresses to a specific port of
the switch are stored. The address / port mapping table is typically generated and main-
tained automatically by the switch through a self-learning process. Incoming data pack-
ages are analyzed, filtered and forwarded directly to the appropriate port by using this as-
signment table based on their destination address. The incoming data package is sent to
all ports, if there is no corresponding entry in the assignment table for a destination ad-
dress. If a destination address answers, the assignment table is complemented with this
destination address as well as the associated port.

3.6 Store-and-forward switching mode

In "Store and Forward" mode, the ETHERNET switch caches the entire data telegram,
checks it for errors (CRC checksum) and if there are no errors, puts it in a queue. Subse-
quently, the data telegram (MAC table) is selectively forwarded to the port that has ac-
cess to the addressed node.
The time delay required by the data telegram to pass the store-and-forward switch de-
pends on the telegram length.
Advantage of "Store and Forward": The data telegrams are checked for correctness and
validity. This prevents faulty or damaged data telegrams from being distributed via the
network.

3.7 Line Depth in PROFINET

Line depth (cascading) is the number of all switches in a communication path.
The maximum line depth depends on the send cycle.
Note
Observe line depth!
Observe the maximum line depth for switches in Store-and-Forward mode according to
the "Topology Check" section of PI-PROFINET Commissioning Guideline
(PROFINET_Commissioning_8081)(ü www.profibus.com).
3.8 Port Speed & Duplex Mode
After a cable is plugged into a specific port, the system uses auto negotiation to deter-
mine the transmission mode for the new twisted pair connection:
If the connected device does not support auto negotiation or has auto negotiation dis-
abled, an auto sensing process is initiated to select the speed and set the duplex mode to
half duplex.
Product manual | Version: 1.0.0
Industrial Eco Switch
Overview
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