Jetter JC-120MC, Руководство пользователя

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JC-120MC Programming
10.15.3 Modbus/TCP client with STX variables
The Modbus/TCP client included in JC-120MC supports only Class 0
Conformance.
In this class, commands for reading and writing multiple registers are used.
One frame transmits up to 125 registers of 16 bits width.
As protocol ID, "0" is used. Assignment of transmitted and received frames is
carried out using the transaction ID.
This chapter describes how to carry out noncyclical or cyclical transmission to
a Modbus/TCP server using STX functions.
Connections to eleven different Modbus/TCP servers may be opened at the
same time.
Functions
ModbusReadReg()
and
ModbusWriteReg()
are used to
establish a noncyclical transmission channel to a Modbus/TCP server.
These functions copy data between registers of a Modbus/TCP server and
STX variables. They establish a connection to the specified Modbus/TCP
server, transmit the desired data and clear down the connection again.
If RemoteScan has already established a connection for cyclical data
transmission, this connection will be used. Setting up and clearing down the
connection is, therefore, not required.
Cyclical data transmission is made through the configurable function
RemoteScanConfig() . The data are cyclically transmitted from and to the
Modbus/TCP servers by means of STX variables.
Only one connection is established to each Modbus/TCP server (IP address
and port) irrespective of the number of communication units which have been
configured on this server.
If several communication units are configured on one Modbus/TCP server,
accesses are serialized since servers often do not support command
pipelining . If several servers have been configured, communication is carried
out in parallel.
Converters from Modbus/TCP to Modbus RTU use the Unit ID for addressing
the Modbus RTU servers. For this reason, the Unit ID can be set.
Introduction
Number of possible
connections
Noncyclical data
transmission
Cyclical data
transmission
Unit ID