Omega CN1166 manual Introduction, Modbus Functions Supported, Message Formats

Page 55

4MODBUS COMMUNICATIONS

4.1INTRODUCTION

This Section specifies the MODBUS communications protocol as implemented on the 161 -DIN Ramp/Soak Profile Controller.

Certain restrictions have been imposed upon this implementation:

(i)Baud rates may be set to 1200, 2400, 4800 and 9600 only

(ii)Support for multi-parameter Writes is limited to support of the Multi-word Write Function (Number 16) but will permit writing of one parameter only per message

(iii)The multi-parameter Read function supports a maximum of 10 parameters in one message.

4.2MODBUS FUNCTIONS SUPPORTED

In the following list, the original Gould MODBUS function names have been used, followed by the JBUS names in italics, where such an equivalence exists. The MODBUS Function number follows the names.

A	Read Coil Status (Read n Bits)	01/02
B	Read Holding Registers (Read n Words)	03/04
C	Force Single Coil (Write 1 Bit)	05
D	Preset Single Register (Write 1 Word)	06
E	Loopback Diagnostic Test	08
F	Preset Multiple Registers (Write n Words)	16

The instrument will identify itself in reply to a Read Holding Registers message which enquires the values of parameter numbers 121 & 122, as specified in the CNOMO documentation, and MODBUS Function 17 (Report Slave ID) will not be supported.

4.3MESSAGE FORMATS

The first character of every message is an instrument address. The valid range of such an address is 0 to 255. The second character is always the Function

O077-4

Volume II

4-1

Image 55

Contents Page Page RAMP/SOAK Profile Volume Operating Instructions Volume Installation & Configuration InstructionsContents PANEL-MOUNTING the Controller Unpacking ProcedureConnections and Wiring Rear Terminal Connections RTD Inputs Mains Line Input2 24V Nominal AC/DC Supply Thermocouple InputSSR Drive Outputs Linear InputsRemote Run/Hold Input Relay Outputs11 RS485 Serial Communications Link DC OutputsRemoving the Profile Controller from ITS Housing Internal Links and SwitchesRemoving the Output 2/Output 3 Option PCBs REMOVING/REPLACING the Output 2/OUTPUT 3 Option PCBs Replacing the Instrument in ITS HousingInput Type Selection of Input Type and Output 1 TypeCPU PCB Relay/SSR Drive/Solid State Output Primary Output Output 1 TypeOutput 2 TYPE/OUTPUT 3 Type Hardware Definition Code Entry Into Configuration ModeWit h Hardw are Definit ion Code displayed Configurat ion ModeHardware Definition Code Input/Output Type Selection Option SelectionWit h Hardw are Definit ion Code displayed Configuration Mode ParametersParameter AL1 OFF, AL2 OFF Parameter Page Exit from Configuration Mode Base Mode Alphabetic Index Controller SET-UP ModeProgram Definition Mode CREATING/EDITING a Program Modbus CommunicationsDisplay Sequence no Program Running Base ModeAborting a Program Starting a ProgramPutting a Program in Hold Releasing a Program from HoldRead Only whilst Program is running/held Display Sequence Program RunningPRE-TUNE Feature RaPID Control FeatureIndication of PRE-TUNE and RaPID Status Engaging Both PRE-TUNE and RaPID FeaturesRaPID Status when Hardware Definition Code has the following significance Viewing the Hardware Definition CodePress till front panel shows Press or to change display to Manual ControlController SET-UP Mode Lower display = Parameter Details Parameter Function Adjustment Range Default ValueON/OFF Parameter Function Adjustment Range Default Value Power Alarm Operation Deviation When this display shows Exit from Controller SET-UP ModeEntry Program Definition Mode CREATING/EDITING a ProgramBasic Guidelines Creating a ProgramTo make a Soak segment Defining Segments Rate ModeDefining Segments Time Mode Program Options T p o i n t Guaranteed Soak BandSegment Event Status Press key To display Exit from Program Define Mode Default Values and Adjustment RangesModbus Functions Supported IntroductionMessage Formats CRC16 Read Coil Status Read n Bits 01/02Force Single Coil Write 1 Bit Read Holding Registers Read n Words 03/04Loopback Diagnostic Test Preset Single Register Write 1 Word 06 BPreset Multiple Registers Write n Words 16 B CRC16 Calculation Error and Exception ResponsesReversed BIT Order Used Bit Parameters Controller Status Byte Parameter NumbersController Parameters Word ParametersInstrument ID Parameters Volume O077-4 Profiler Status Byte Profiler CommandsGeneral Universal InputInput Range Remote RUN/HOLD Input Option Solid State OutputRelay SSR Drive/TTLTypes Available Relay, SSR drive, solid state and DC Solid State SSR Drive/TTL Loop Control Alarm ControlReference Conditions PerformancePerformance Under Reference Conditions S077-A Volume See Performance EnvironmentalPhysical Appendix B Summary of Displays Program Define Mode Parameters Configuration Mode Parameters AppendixC RaPID Control Feature AT OFF Alphabetical Index S077-IDX Volume Making a Soak Segment S077-IDX Volume Unpacking Procedure Word Parameters II/4-8