Automationdirect.com DL05, Руководство пользователя

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CPU Specifications
and Operation
4–41
CPU Specifications and Operation
Network Master Operation
This section describes how the DL05 can communicate on a MODBUS or Direct NET
network as a master. For MODBUS networks, it uses the MODBUS RTU protocol,
which must be interpreted by all the slaves on the network. Both MODBUS and
Direct Net are single master/multiple slave networks. The master is the only member
of the network that can initiate requests on the network. This section teaches you how
to design the required ladder logic for network master operation.
Slave #1 Slave #3
Master
MODBUS RTU Protocol, or DirectNET
Slave #2
When using the DL05 PLC as the master station, simple RLL instructions are used
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 will 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, which goes to the port.
Slave
Master
WX (write)
RX (read)
Network
The following step-by-step procedure will provide you the information necessary to
set up your ladder program to receive data from a network slave.