Hitachi HIDIC EH-150 Applications Manual page 78

In the H series CPU link, transmission data output from any PLC is broadcast to the link areas of the other PLCs
on the network. Thus, the same data is shared in identical WL areas from any CPU.
On the other hand, in the link system using the EH-RMD, the transmission data of each EH-RMD is collected in
one master station. In this example, PLC1 is the master station.
Use the ladder program of PLC1 to copy the data to the transmission area in order to send it to PLCs 2, 3, and 4. It
is noted that, in this method, a transmission area is required for each PLC.
Therefore, when sharing data using the EH-RMD, the data size will be limited to the value obtained from
(formula 1).
256 words/number of (slave) EH-RMDs = number of words that can be shared by each EH-RMD
(formula 1)
The transmission area for each EH-RMD must be assigned so that it does not exceed the value calculated by
(formula 1).
In the configuration shown in Figure 9.2, the maximum data size that can be shared is 85 words (1 word left); thus
the transmission size for each EH-RMD should be assigned within this range.
Note, however, that this is done in order to control the shared data centrally by the master station. It is also
possible to configure an individual system where a slave station is used as the master to use its vacant area.
9-3
Chapter 9 Slave Mode