Troubleshooting guide

Contents v
April 1998 Rev. 1
Contents
REVISION HISTORY......................................................................................................................IV
Chapter 1 - Overview ...............................................................................................1
SCOPE................................................................................................................................................1
MODBUS® NETWORK ...................................................................................................................1
CONFIGURATION............................................................................................................................1
FUNCTIONS IMPLEMENTED ........................................................................................................1
TS310 DATA BASE...........................................................................................................................1
TS310 MODBUS® DATA BASE......................................................................................................2
DIGITAL POINTS .............................................................................................................................2
Coil Status ......................................................................................................................................2
Input Status.....................................................................................................................................2
ANALOG POINTS.............................................................................................................................3
Holding Registers ...........................................................................................................................3
Input Registers................................................................................................................................3
Chapter 2 - Description............................................................................................5
MODBUS® MESSAGE PROTOCOL...............................................................................................5
MODE OF TRANSMISSION, RTU MODE .....................................................................................5
GENERAL MODBUS® MESSAGE FORMATS.............................................................................5
SAMPLE MESSAGE CONTENT .....................................................................................................6
MESSAGE FIELD DEFINITIONS....................................................................................................7
Station Address Field .....................................................................................................................7
Function Code Field .......................................................................................................................7
Data Fields......................................................................................................................................7
Checksum Field..............................................................................................................................7
MODBUS® FUNCTION DESCRIPTIONS......................................................................................8
Read Coil Status (Function Code 01)............................................................................................8
Read Input Status (Function 02)..................................................................................................10
Read Holding Registers (Function Code 03) (Read/Write Integer) ...........................................10
Read Input Registers (Function Code 04) (Read Integer)..........................................................11
Force Single Coil (Function Code 05).........................................................................................11
Preset Single Register (Function Code 06) .................................................................................12
Loop-Back Diagnostic Test (Function 08)..................................................................................12
ERROR DETECTION & EXCEPTION RESPONSES...................................................................13
Transmission Errors......................................................................................................................13
Exception Responses....................................................................................................................13
CRC CHECKSUM CALCULATION..............................................................................................13
CRC Error Check for RTU Mode.................................................................................................14
RECOMMENDED PARAMETERS FOR MODBUS® FUNCTIONS...........................................14
MODBUS® REFERENCING OF TS310 POINTS..........................................................................14
TS310 MODBUS® DATA DEFINITIONS.....................................................................................14
Coil Status ....................................................................................................................................15
Input Status...................................................................................................................................15
Holding Registers .........................................................................................................................16
Input Registers..............................................................................................................................19