Mitsubishi MELSEC-A Series Reference Manual page 75

4. COMPOSITION OF A THREE-TIER SYSTEM
4.4 Three-Tier System using the MELSECNET/B Data Link System
When the second and third tiers are configured with MELSECNET/B data link system,
connect the stations using shielded twisted pair cables.
4.4.1 System configuration
Fig 4.5 shows the configuration of the three-tier system.
(a) Up to 31 local and remote I/O stations can be connected to a master station for
the second tier.
(b) For the third tier, up to 31 local and remote I/O stations can be connected to the
master station, which is the local station for the second tier.
Fig 4.5 Three-tier system configured with MELSECNET/B data link system
POINT
(1) Remote I/O stations cannot be connected in MELSECNET
(2) MELSECNET/B data link system has no restriction on the order of stations
(including master stations).
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mode.