Micromod MOD: MODBUS RTU Communications Guide - Manual (Page 3)

MODBUS RTU
CONTENTS
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CONTENTS
Page
OVERVIEW ......................................................................................................................................................... 1
HARDWARE REQUIREMENTS.......................................................................................................................... 2
SERIAL INTERFACE CONSIDERATIONS .................................................................................................... 2
CABLE REQUIREMENTS .............................................................................................................................. 2
COMMUNICATIONS MODE........................................................................................................................... 2
RS-232 INTERFACE....................................................................................................................................... 3
RS-422 INTERFACE....................................................................................................................................... 3
RS-485 INTERFACE....................................................................................................................................... 3
BIAS RESISTORS .......................................................................................................................................... 3
TERMINATION RESISTORS ......................................................................................................................... 3
SOFTWARE BASICS .......................................................................................................................................... 5
MASTER/SLAVE RELATIONSHIP ................................................................................................................. 5
MESSAGE RESPONSE TIMES ..................................................................................................................... 5
INSTRUMENT RESPONSE TIMES TO HOST COMMANDS ........................................................................ 5
SOFTWARE DRIVERS................................................................................................................................... 6
MODBUS WITH MODCELL MLP AND MOD30ML ............................................................................................. 7
STANDARD PROTOCOL ............................................................................................................................... 7
EXTENDED PROTOCOL ............................................................................................................................... 7
MOD 30ML COMMUNICATION CHANNELS................................................................................................. 7
USING ML AND CL BLOCKS:............................................................................................................................. 8
DIRECTING DATA WITH ML AND CL BLOCKS............................................................................................ 8
BLOCK CONNECTIONS ................................................................................................................................ 9
USING MODBUS MODULES:........................................................................................................................... 10
MODULE LOCATION ................................................................................................................................... 10
THE RS-485’S TERM (MASTER/SLAVE) SWITCH ..................................................................................... 10
THE COM DEFAULTS SWITCH .................................................................................................................. 10
THE HIGH AND LOW SWITCHES ............................................................................................................... 10
MODBUS MASTER ........................................................................................................................................... 12
MASTER REQUIREMENTS ......................................................................................................................... 12
DATA CONVERSION ................................................................................................................................... 12
SCALER BLOCK........................................................................................................................................... 12
INPUT CONVERT BLOCK ........................................................................................................................... 13
OUTPUT CONVERT BLOCK ....................................................................................................................... 13
MODBUS WITH COMMANDER SERIES INSTRUMENTS .............................................................................. 14
SCALING ANALOG VALUES ....................................................................................................................... 14
COMMUNICATIONS CONFIGURATION ..................................................................................................... 14
CONNECTION WITHIN THE NETWORK .................................................................................................... 14
HOST CONFIGURATION EXAMPLES ............................................................................................................. 15
MODBUS WITH FIX AND COMMANDER 150 ............................................................................................. 15
MODBUS WITH FIX AND COMMANDER 300 ............................................................................................. 16
MODBUS WITH INTOUCH AND COMMANDER 300 .................................................................................. 17
MODCELL MLP WITH TCP QUICKPANEL.................................................................................................. 18
PLC & Protocols ........................................................................................................................................ 18
Tags .......................................................................................................................................................... 18
Addressing ................................................................................................................................................ 18
Scaling....................................................................................................................................................... 19
MOD30ML AND MODCELL MLP REFERENCE TABLES ................................................................................ 20
WIRE CONNECTIONS...................................................................................................................................... 22
MODBUS MODULE TROUBLESHOOTING WITH MOD30ML AND MODCELL MLP ..................................... 23
GLOSSARY ....................................................................................................................................................... 25