Mitsubishi MELSEC-A Series Reference Manual page 86

5. SPECIFICATIONS
(2) Communication between the master station and all local stations
Link relays (B) and link registers (W) are used for communication between the master
station and a local station or communication between local stations.
Link relays (B) and link registers (W) are used by the master station and all local
stations in common.
Link relays (B) and link registers (W) send data to other station, using the range
assigned to the host station with a link parameter.
• Link relays (B) are internal relays for the data link and are used for sending ON/
OFF data.
• Link registers (W) are data registers for the data link and are used for sending 16-
bit data.
• Link relays (B) and link registers (W) handle different types of data.
However, the range of communicating with other stations in the data link system is
the same.
The following explains the range in which communication is possible with link relays
(B) and link registers (W) when using the MELSECNET mode.
In the MELSECNET
function is basically the same, stations with which communication is possible partly
differ between the range assigned to the first half of the link parameter and the range
assigned to the second half of the link parameter. (For details, refer to Section 5.3.8.)
(a) Two-tier system configuration
1) The master station and local stations can read the entire range of link relays
(B) and link registers (W) assigned by the link parameter.
The read/write range of each station is explained by showing Fig 5.1 as an
example.
mode and MELSECNET
Fig 5.1 Two-tier system configuration
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composite mode, although the