Model: CDU-LCD
Doc. Ref. no.:- mMP/om/601
Issue no. 00.06
User’s Manual
Page 21 of 32
8. COMMUNICATION PROTOCOL
– MODBUS RTU
8.1 Introduction
The unit can be connected in RS-485 communication data link either in multi drop or
repeat mode. Each unit must have unique Serial Number. Entire range of addresses
(1 to 247) may be used. Before starting any communication, choose a baud rate
compatible to the host computer. The serial protocol used is MODBUS RTU.
8.2 Function Code for Modbus
CODE
NAME
Function
03
Read Holding registers
Use to read PV.
04
Read input registers
Use to read programmable registers
06
Preset Single register
Use to write programmable register
16
Preset Multiple register
Use to write programmable register(Time, Serial
No. etv)
Table 7
The error checking field contains a 16-bit value implemented as two eight-bit bytes.
The error check value is the result of a Cyclical Redundancy Check (CRC)
calculation performed on the message contents.
8.3 Temperature
Paramet er
(PV displ a y)
Setting Name & Description
Default
Value
Modbus
Absolute
Addresses
Name
40001
Set Point
High
Adjust SET POINT High value
0 to 600 For °C - 0.1 degree Resolution
250
40002
Set Point
Low
Adjust SET POINT Low value
0 to 600 For °C - 0.1 degree Resolution
150
40003
Alarm High
Set Alarm Type for Alarm HIGH
0 : HI(High)
1 : LOW(Low)
2 : DIS(Disable)
HIGH
40004
Alarm Low
Set Alarm Type for Alarm LOW
0 : HI(High)
1 : LOW(Low)
2 : DIS(Disable)
LOW
40008
Band
Set band for data logging
0 to 100 For °C - 0.1 degree Resolution
5
40013
Sensor
Set Sensor Break Value
LAST
