xLadder user manual-V2.0.0.6

 1 Port doesn ’ t exist

 2 Port isn ’ t enabled

 3 Communication task queue is full

 4 Table error

 5 Sent data error

 6 Timeout

 7 Received data error

 8 Receive data check error

The use of free port communication instructions will be illustrated with

examples in the additional chapter.

MODBUS communication protocol

MODBUS protocol is a common language used in electronic controllers.Different

devices can communicate with each other by using the MODBUS communication protocol.

It has become a general industrial standard.You can use it to connect different

devices.

This protocol defines a message structure, no matter what network they use to

communicate.It describes the process of controller requesting to access other

devices.It has formulated message domain structure and the common format of the

content.

MODBUS network protocol determines that each controller should know its address.

It identifies the messages sent from different addresses and decides what action

to take.The controller generates feedback information, the format of the

information is the information format of MODBUS.It is issued through the MODBUS

protocol.

MODBUS address usually contains data type and offset.MODBUS address contains a

total of 5 characters.The first character represents the data type and the other

four characters represent the correct values in the data type.

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