ProSoft Technology PLX3x Series, Руководство пользователя

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MBTCP Protocol PLX3x Series ♦ Multi-Protocol Gateways
User Manual
Page 112 of 215 ProSoft Technology, Inc.
January 25, 2018
MBTCP Command List Error Codes
The PLX3x gateway detects these command-specific error codes during initial
command list loading at PLX3x gateway power-up or reset and are stored in the
Command Error List memory region.
Code Description
-40 Too few parameters
-41 Invalid enable code
-42 Internal address > maximum address
-43 Invalid node address (<0 or >255)
-44 Count parameter set to 0
-45 Invalid function code
-46 Invalid swap code
6.4 MBTCP Reference
6.4.1 About the Modbus Protocol
Modbus is a widely-used protocol originally developed by Modicon in 1978. Since
that time, the protocol has been adopted as a standard throughout the
automation industry.
The original Modbus specification uses a serial connection to communicate
commands and data between master and server devices on a network. Later
enhancements to the protocol allow communication over Ethernet networks using
TCP/IP as a "wrapper" for the Modbus protocol. This protocol is known as
Modbus TCP/IP.
Modbus TCP/IP is a client/server protocol. The master establishes a connection
to the remote server. When the connection is established, the master sends the
Modbus TCP/IP commands to the server. The PLX3x gateway simulates up to 30
masters, and works both as a master and a server.
Aside from the benefits of Ethernet versus serial communications (including
performance, distance, and flexibility) for industrial networks, the Modbus TCP/IP
protocol allows for remote administration and control of devices over an Internet
connection. It is important to note that not all Internet protocols are implemented
in the module; for example, HTTP and SMTP protocols are not available.
Nevertheless, the efficiency, scalability, and low cost of a Modbus TCP/IP
network make this an ideal solution for industrial applications.
The PLX3x gateway acts as an input/output module between devices on a
Modbus TCP/IP network and the Rockwell Automation backplane and processor.
The module uses an internal database to pass data and commands between the
processor and the master and server devices on the Modbus TCP/IP network.