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Communications Mechanism Section 8-1
Polling Node Each Controller Link Network always has a Unit that controls communications
within the network. This Unit is called the “polling node.” Normally, the node
that has the smallest node address in the network is the polling node (see
note). All Units at nodes other than the polling node are called “polled nodes”
(or polled units). The polling node controls the token, checks the network, and
performs other relevant tasks. Should the polling node break down, the node
with the next smallest node address is automatically selected as the polling
node to prevent the entire network from shutting down.
Note The node with the smallest node address is not always the polling node,
depending on the Unit start-up sequence, models, settings, and Unit status.
When the polling node breaks down, the next polling node is temporarily dis-
connected from the network, reconstructs the network, and then reconnects
to the network. Polling nodes remain connected to the network.
8-1-2 Setting the Polling and Polled Nodes
Use the Programming Device for the PLC to set Units as polling node or
polled node in the DM Parameter Area.
CS/CJ-series Controller Link Units
C200HX/HG/HE Controller Link Units
CVM1 and CV-series Controller Link Units
CQM1H-series Controller Link Units
Check
Token circulation
cycle
Polling cycle
Communications cycle time
Check
Polling cycleToken circulation
cycle
Communications cycle time
0 000000000––000–
1514131211109876543210
DM 30000 + 100 × N
N: Unit number
–: Other settings
Polling node/polled node bit
0: Polling node
1: Polled node
Operating level 0
Polling node/polled node bit
0: Polling node
1: Polled node
–: Other settings
0 –0–000
000––0000
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
DM 6400
DM 6420
Operating level 1
0 0000000
15 14 13 12 11 10 9 8
00––000–
76543210
DM 2000 + 100 × N
N: Unit number
–: Other settings
Polling node/polled node bit
0: Polling node
1: Polled node
Polling node/polled node bit
0: Polling node
1: Polled node
–: Other settings
0 –0–000
000––000
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
DM 6400
0