Abstract
This document describes using the Modbus Universal Master driver to communicate with devices/PLC's that can be a Modbus RTU Slave
Products
Red Lion Controls CR1000 Human Machine Interface (HMI), CR3000 HMI, Data Acquisition (DA10, DA30), Data Station Plus, FlexEdge™ (DA50A, DA70A), G3 HMI, G3 Kadet HMI, Graphite® Controller, Graphite HMI, Modular Controller, and Productivity Station™
Use Case
Communicating with devices that can talk Modbus RTU via RS485
Required Software:
Crimson 3.0, Crimson 3.1 & Crimson 3.2
Crimson Communication Configuration:
In Crimson 3.x, go to RS 485 comms port - >You will need to pick Modbus Universal Master driver so that Red lion can be a Modbus RTU Master. Make sure port settings are entered correctly
Once you pick the driver, a new device PLC1 will be created automatically and that's where you define the drop number(also known as device ID or Slave ID in automation world) of the slave device. Further down in this section, there will be a setting called ping holding register under Protocol options. Ping holding register defaults to 1 which means that the redlion device will look for a 16 bit holding register 40001/400001 in the slave device. If this address is not available in the slave device, you can use another address say for example you have a 40016/400016 register in the slave device in which case you will set ping holding register to 16. If there aren't any holding registers available in the slave device, you need to set this to 0 for communication to be established successfully.
Wiring:
Part number CBLGEN03 in the link below has pin out of RS485 connection coming out of the redlion device.
Pin 1 and 2 are typically - and + while Pin 6 is common. When the wiring is correct, you will see both Red and Green LED blink rapidly. If you see solid Red and blinking green, it means polarity need to be reversed and as a result you should swap your Pins 1 and 2.
You can use any of the four combinations for 2 wire RS485 wiring. Pins 1 and 2 or Pins 2 and 7 or Pins 7 and 8 or Pins 1 and 8 since Pins 1 and 7 are internally jumpered and similarly Pins 2 and 8 are also internally jumpered.
Pin 5 (TxEN) is used only for Allen Bradley DH485 communication and should be ignored for Modbus
For 4 wire RS485 communication, you will use Pins 1, 2, 3 and 4 with Pin 6 being used for Common.
Crimson Tag Mapping:
In the data tags section, create a new numeric or flag tag, go to source -> data source -> click on Internal and pick PLC1 from the drop down and make sure you map it to the correct address.
We use 6 digit modbus addressing. The difference between 5 digit and 6 digit is that there is an extra 0 after the prefix .
For example, 40001 is the same as 400001
Also, 6 digit modbus addressing means extended modbus addressing range from 400001 to 465535, 300001 to 365535, 100001 to 165535 and 000001 to 065535
We use 1 based modbus addressing. Check with slave device's support or in their manual if they are 0 based or 1 based. If it's 0 based, then all the addresses will be offset by 1.
For example, if they are 0 based and use 5 digit modbus addressing, then 40000 in their addressing would be 400001 in Crimson.
L4 holding registers should used only for Enron Modbus which very few devices in the automation world supports.
If you are looking to map to a 32 bit floating point input register or holding register, you need to pick data type as " Word as Real" after picking data item 3 or 4 for input registers or holding registers.
If you are looking to map to a 32 bit signed input register or holding register, you need to pick data type as " Word as long" after picking data item 3 or 4 for input registers or holding registers.
Disclaimer
It is the customer's responsibility to review the advice provided herein and its applicability to the system. Red Lion makes no representation about specific knowledge of the customer's system or the specific performance of the system. Red Lion is not responsible for any damage to equipment or connected systems. The use of this document is at your own risk. Red Lion standard product warranty applies.
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