ICON ProCon D400 Series, Operating Manual

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D400 Series Operating Manual
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MODBUS RTU General Information
Overview
The hardware version number of this document is V2.0; the software version number is V5.9 and above. This document describes the
MODBUS RTU interface in details and the target object is a software programmer.
MODBUS Command Structure
Data format description in this document;
Binary display, suffix B, for example: 10001B
- decimal display, without any prefix or suffix, for example: 256
Hexadecimal display, prefix 0x, for example: 0x2A
ASCII character or ASCII string display, for example: “YL0114010022”
Command Structure
The MODBUS application protocol defines the Simple Protocol Data Unit (PDU), which is independent of the underlying communication
layer.
Figure 1: MODBUS Protocol Data Unit
MODBUS protocol mapping on a specific bus or network introduces additional fields of protocol data units. The client that initiates the
MODBUS exchange creates the MODBUS PDU, and then adds the domain to establish the correct communication PDU.
Figure2: MODBUS architecture for serial communication
On the MODBUS serial line, the address domain contains only the slave instrument address. Tips: The device address range is 1...247. Set
the device address of the slave in the address field of the request frame sent by the host. When the slave instrument responds, it places its
instrument address in the address area of the response frame so that the master station knows which slave is responding. Function codes
indicate the type of operation performed by the server. CRC domain is the result of the “ redundancy check” calculation, which is executed
according to the information content.