Mitsubishi MELSEC-A Series Reference Manual page 51

4. COMPOSITION OF A THREE-TIER SYSTEM
In the three-tier system, optical fiber cables and coaxial cables can be used together for
the second and third tiers.
Combinations of the optical fiber cables and coaxial cables for each tier are shown below.
POINT
(1) In MELSECNET data link system, up to three tiers can be configured.
(2) Remote I/O stations cannot be connected if the MELSECNET
used.
4 - 3
mode is