Veris Industries FSRxxxx SERIES Install - Manual (Page 40)

FSRxxxx SERIES
Z205739-0D PAGE 40 ©2013 Veris Industries USA 800.354.8556 or +1.503.598.4564 / [email protected] 05131
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TM
INSTALLATION GUIDE
Communications Protocols
1. FSR1 Modbus
Available Data Formats
Bits Bytes
Modbus
Registers
Long Integer 32 4 2
Single Precision IEEE754 32 4 2
Double Precision IEEE754 64 8 4
Table A-3.1 - Available Data Formats
2. Modbus Register / Word Ordering
Each Modbus Holding Register represents a 16-bit integer value (2 bytes). The
official Modbus standard defines Modbus as a ‘big-endian’ protocol where the most
significant byte of a 16-bit value is sent before the least significant byte. For example,
the 16-bit hex value of ‘1234’ is transferred as ‘12’ ‘34’.
Beyond 16-bit values, the protocol itself does not specify how 32-bit (or larger)
numbers that span over multiple registers should be handled. It is very common
to transfer 32-bit values as pairs of two consecutive 16-bit registers in little-endian
word order. For example, the 32-bit hex value of ‘12345678’ is transferred as ‘56’ ‘78’
‘12’ ‘34’. Notice the Register Bytes are still sent in big-endian order per the Modbus
protocol, but the Registers are sent in little-endian order.
Other manufactures, store and transfer the Modbus Registers in big-endian word
order. For example, the 32-bit hex value of ‘12345678’ is transferred as ‘12’ ‘34’
‘56’ ‘78’. It doesn’t matter which order the words are sent, as long as the receiving
device knows which way to expect it. Since it’s a common problem between devices
regarding word order, many Modbus master devices have a configuration setting
for interpreting data (over multiple registers) as ‘little-endian’ or ‘big-endian’ word
order. This is also referred to as swapped or word swapped values and allows the
master device to work with slave devices from different manufactures.
If, however, the endianness is not a configurable option within the Modbus master
device, it’s important to make sure it matches the slave endianess for proper
data interpretation. The meter actually provides two Modbus Register maps to
accommodate both formats. This is useful in applications where the Modbus Master
cannot be configured for endianness.
Data
Component
Name
MODBUS Registers
Available Units
Long
Integer
Format
Floating Point
Single
Precision
Format
Double
Precision
Format
Signal
Strength
40100 - 40101 40200 - 40201 40300 - 40303
Flow Rate 40102 - 40103 40202 - 40203 40304 - 40307 Gallons, Liters,
MGallons, Cubic
Feet, Cubic Meters,
Acre Feet, Oil Barrel,
Liquid Barrel, Feet,
Meters, Lb, Kg, BTU,
MBTU, MMBTU, TON,
kJ, kW, MW
Per Second, Minute,
Hour, Day
Net Totalizer 40104 - 40105 40204 - 40205 40308 - 40311
Positive
Totalizer
40106 - 40107 40206 - 40207 40312 - 40315
Negative
Totalizer
40108 - 40109 40208 - 40209 40316 - 40319
Temperature
1
40110 - 40111 40210 - 40211 40320 - 40323 °C
Temperature
2
40112 - 40113 40212 - 40213 40324 - 40327 °C
Table A-3.2 - MODBUS Register Map for ‘Little-endian’ Word Order Master Devices
For reference: If the Net Totalizer = 12345678 hex:
Register 40102 would contain 5678 hex (Word Low)
Register 40103 would contain 1234 hex (Word High)
Data
Component
Name
MODBUS Registers
Available Units
Long
Integer
Format
Floating Point
Single
Precision
Format
Double
Precision
Format
Signal Strength 40600 - 40601 40700 - 40701 40800 - 40803
Flow Rate 40602 - 40603 40702 - 40703 40804 - 40807 Gallons, Liters,
MGallons, Cubic
Feet, Cubic
Meters, Acre
Feet, Oil Barrel,
Liquid Barrel,
Feet, Meters, Lb,
Kg, BTU, MBTU,
MMBTU, TON, kJ,
kW, MW
Per Second,
Minute, Hour,
Day
Net Totalizer 40604 - 40605 40704 - 40705 40808 - 40811
Positive Totalizer 40606 - 40607 40706 - 40707 40812 - 40815
Negative Totalizer
40608 - 40609 40708 - 40709 40816 - 40819
Temperature 1 40610 - 40611 40710 - 40711 40820 - 40823 °C
Temperature 2 40612 - 40613 40712 - 40713 40824 - 40827 °C
Table A-3.3 - D(X)TFX MODBUS Register Map for ‘Big-endian’ Word Order Master Devices
For reference: If the Net Totalizer = 12345678 hex:
Register 40602 would contain 1234 hex (Word High)
Register 40603 would contain 5678 hex (Word Low)