1. DT80 range Modbus capability
David Williams
Product Development Manager
23 March 2010

2. Introduction to Modbus
What is Modbus?
Is an serial data protocol for transferring data between intelligent devices.
Widely used in industrial sector
Designed to be scalable in size and complexity.
Supported in SCADA (Supervisory Control And Data Acquisition) applications
Has a Master (Client) that requests data from Slave (Server) devices

3. Introduction to Modbus
Modbus can operate using a broad range of communications media.
Serial connection are typically RS232, RS422 or RS485
TCP/IP network, which can use a variety of physical link types e.g. Ethernet wireless, fibre-optic, serial (PPP)
There are two methods of data transfer
Modbus RTU (Remote Telemetry Unit)
Binary data in packet format
Most common implementation
Modbus ASCII
Plain text in packet format (Little used)

4. Introduction to Modbus
Modbus Serial
One master per network
Each network can have up to 247 slave devices
1 slave device for RS232
Each slave device has a unique address (1 to 247)
Modbus TCP/IP
Multiple masters on one network
Slave devices identified by TCP/IP address.

5. Introduction to Modbus
The master device requests data from the slave
Message includes;
Slave address
Function codes;
0 = Read a coil (e.g. Read / write the state of a digital channel)
1 = Read state
3 = Input register (Read a register)
4 = Output register (Read or write to a register.)
Starting address of registers to be accessed
Number of registers
16 bit check sum

6. Introduction to Modbus
Slave device will respond only to messages direct to it.
Slave devices can have up to registers
Registers can be either coils (bit state) or data
Data can be of types;
Signed 16 bit integer
Unsigned 16 bit integer
Signed 32 bit integer
Unsigned 32 bit integer
32 bit floating point number
Maximum message length is 255 bytes
This means you need to understand the device configuration and mapping

7. DT80 Range Modbus capability
Generic implementation
No special drivers required for SCADA packages
Ease of integration into existing SCADA systems
Supports standard Modbus data types
Flexible communications
Can support non standard baud rates and other communications settings (Parity, TCP/IP ports etc)
Can be simultaneously connected to more than one Modbus network
Can be a master and slave simultaneously on different networks

8. DT80 Range Modbus capability
Example;
Can be a master on an serial sensor port RS485 network and a slave on the RS232 host port
Can be a master and a slave on a TCP/IP network

9. DT80 Range Modbus capability
The DT80 supports Modbus master or slave modes over
RS Serial sensor port and Host port
RS Serial sensor port
RS Serial sensor port
TCP/IP - Ethernet or PPP
On a TCP/IP network a DT80 can be both a master and a slave device at the same time.

10. DT80 Range Modbus capability
Unusual capabilities
Back filling data in to SCADA systems
SCADA systems are real time. If the network or power fails then data is lost. The DT80 having independent power will keep data that can be recovered latter.
Independent alarming.
The DT80 has the capability to send alarms independent of SCADA system
Gateway
Modbus to Modbus
SDI-12 to Modbus
Serial to Modbus
CAN to Modbus (e.g. OBDII, J1939)

11. DT80 Range Modbus capability
Unusual capabilities
FTP Client - Can push data to a site
FTP Server - Can serve data when requested
High quality web interface built in as standard
Custom web pages
Allows real time inter logger calculations and data exchange.

12. DT80 Range Modbus Slave configuration
Introduced in V6.02 firmware (May 2006)
Modbus registers mapping
Channel variables Registers 1 to 1000
System variables Registers 4001 to 4053
Digital I/O and relay - Registers 8000 to 8009
Note: Modbus master can access digital i/o directly
Data types supported
Signed 16 bit integer
Unsigned 16 bit integer
Signed 32 bit integer
32 bit floating point number

13. DT80 Range Modbus Slave configuration
Slave commands and settings
SetModBus
Used to set the data type in the registers
Profile settings
Allow the DT80 to be configured to suit Modbus network
Set communications interface to slave mode
Note: Modbus ASCII is not supported

14. DT80 Range Modbus Master configuration
Example of code
Begin“Slave"
SETMODBUS 1..2CV MBI 100 'Configure Modbus registers for temperature readings
RA("B:",Data:NOV:60D)1M
' Measure concrete temperature - 2 thermocouples per channel on CEM20 #1
101*TT(=1CV,"Temp1~DegC",ff2) 'Temperature 1 mapped to MODBus register 1
101TT(=2CV,"Temp2~DegC",ff2) 'Temperature 2 mapped to MODBus register 2
END

15. DT80 Range Modbus Master configuration
Introduced in V8 firmware (March 2010)
New channel type nMODBUS(Options)(=Assign)
Access to the different communications interfaces
1 = Serial sensor port
2 = Host port
4 = TCP/IP

16. DT80 Range Modbus Master configuration
Channel options;
Allow read / access to all Modbus functionality
Assign (Option)
Writing data to single or multiple registers - =x..xxCV
Profile settings
To configure DT80 to match Modbus network
Set communications interface to master mode
Error messages and diagnostics
Full error reporting will 11 new error messages
Diagnostics for Modbus added

17. DT80 Range Modbus Master configuration
Example of code
Begin"Master"
RA1M
'=======================================================
'Read remote temperatures from MODBus slave
' RTU address - AD“myDT80.com.au"
' Register 3 start address 1 - R3:1
' Read consecutive registers to CV's - =1..2CV
' Read MODBus signed integers - MBI
' Integers have been x 100 so we x by
' 3 re-tries - RT3
' 15 second time out - TO15
4MODBUS(AD"myDT80.com.au",R3:1,=1..2CV,MBI,0.01,RT3,TO15,W)
1cv(ff2,"RmtTemp1~DegC") 'Remote Temperature 1
2cv(ff2,"RmtTemp2~DegC") 'Remote Temperature 2
End

18. DT80 Range Modbus applications
Who use Modbus?
Manufacturing
Petrochemical
Chemical
Power
Water
Desalination
Purification
Waste treatment

19. DT80 Range Modbus applications
What can we connect to?
Programmable Logic Controllers (PLC)
Controllers (Ovens, water baths, fridges, freezers etc)
Human Machine Interfaces (HMI)
Analog and digital I/O modules
Smart Sensors
RFID tag readers
Pressure
Supervisory Control And Data Acquisition (SCADA)
Whole new ranges of sensors, devices and applications.

20. DT80 Range Modbus applications
HMI
Allows operator to enter data directly into DT80
Change set points
Batch ID’s
Operator ID
Graphical display of real time data to operator
Indicators
Charts
Mimic type displays.

21. DT80 Range Modbus applications
Dam monitoring
Multiple remote sites (50+)
Mix of sensors
SDI-12
Modbus depth sensor
Vibrating wire piezometers
Remote Network connection via VPN back to central SCADA system
Data is backed up by using dataTaker unload commands to a separate system.

22. DT80 Range Modbus applications
Vehicle location & down time monitoring
In each vehicle
Modbus RTU RFID tag read
Touch screen HMI
DT80
RFID tags distributed around site
If a vehicle has been stationary for more than a set period of time then the driver is required to input a reason why.