Ethernet Communications Modules, 3rd Edition, Rev. D
5-15
Chapter 5: MODBUS TCP for H0/H2/H4-ECOM100
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Network Client (Master) Operation
This section describes how the DL05/06/205/405 CPU can serve as a client on a Modbus TCP
network using the H0/H2/H4 -ECOM100. This section discusses how to design the required
ladder logic for network client operation.
Slave #1
Slave #3
Client
MODBUS TCP Protocol
Slave #2
MODBUS TCP Servers
Slave
Client
WX (write)
RX (read)
Network
When using the ECOM100 as a client on the
network, you use simple RLL instructions to
initiate the requests. The WX instruction initiates
network write operations, and the RX instruction
initiates network read operations. Before executing
either the WX or RX commands, we need to load
data related to the read or write operation onto the
CPU’s accumulator stack. When the WX or RX
instruction executes, it uses the information on the
stack combined with data in the instruction box to
completely define the task.
