Icon Process Controls ProCon DO3000-C Series Quick Start Manual page 18

ProCon — DO3000-C Series
®
Dissolved Oxygen Controller
MODBUS RTU
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.
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.
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.
25-0671 © Icon Process Controls Ltd.
Function Code
Fig.1 : MODBUS Protocol Data Unit
MODBUS SERIAL LINE PDU
Address Field Function Code
Fig.2 : MODBUS Architecture for Serial Communication
Data
Data
MODBUS PDU
CRC
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