EASTRON SDM630 Modbus V2 DIN Rail Smart Meter User Manual

EASTRON SDM630 Modbus V2 DIN Rail Smart Meter

Product Information

Specifications

• Measures: kWh, Kvarh, KW, Kvar, KVA, P, F, PF, Hz, dmd, V, A
• Bi-directional measurement: IMP & EXP
• Two pulse outputs
• RS485 Modbus communication
• Din rail mounting (35mm)
• 80A direct connection
• Accuracy: Better than Class 1 / B

Product Usage Instructions

Unit Characteristics
The unit can measure and display:

• Line voltage and THD% of all phases
• Line Frequency
• Currents, Current demands, and current THD% of all phases
• Power, maximum power demand, and power factor
• Active energy imported and exported
• Reactive energy imported and exported

Password-protected Set-up Screens
The unit has password-protected set-up screens for:

• Changing password
• Supply system selection (1p2w, 3p3w, 3p4w)
• Demand Interval Time (DIT)
• Reset for demand measurements
• Pulse output duration

Pulse Output
This provides two pulse outputs that clock up measured active and reactive energy. The configurable pulse output 1 can be set from the set-up menu.

Start-up Screens
The start-up screens display information about the firmware and perform self-tests before displaying active energy measurements.

Measurements Buttons
The buttons operate as follows:

1. Selects the Voltage and Current display screens
2. Select the Frequency and Power factor display screens
3. Select the Power display screens
4. Select the Energy display screens

Voltage and Current
Each successive pressing of the buttons selects a new range for voltage, current, and THD% measurements.

Frequency, Power Factor, and Demand
Each successive pressing of the buttons selects a new range for frequency, power factor, and maximum power demand measurements.

FAQ (Frequently Asked Questions)

• Q: Can the pulse output constants be adjusted?
  A: The constant of pulse output 2 for import active energy is fixed at 400imp/kWh. However, the configurable pulse output 1 can be adjusted from the set-up menu.

• Q: How can I access the password-protected set-up screens?
  A: To access the set-up screens, enter the correct password and navigate through the options to make desired changes.

• Q: What is the default pulse output width?
  A: The default pulse output width for configurable pulse output 1 is 100ms.

SDM630-ModbusV2
DIN Rail Smart Meter for Single and Three Phase Electrical Systems

• Measures kWh Kvarh, KW, Kvar, KVA, P, F, PF, Hz, dmd, V, A, etc.
• Bi-directional measurement IMP & EXP
• Two pulse outputs
• RS485 Modbus
• Din rail mounting 35mm
• 80A direct connection
• Better than Class 1 / B accuracy

Introduction

• The SDM630-Modbus V2 measures and displays the characteristics of single phase two wires (1p2w), three phase three wires (3p3w,) and three phase four wires(3p4w) supplies, including voltage, frequency, current, power, active and reactive energy, imported or exported. Energy is measured in terms of kWh, kVArh. It follows the calculation mode of net-counting (Total=import-export). Maximum demand current can be measured over preset periods of up to 60 minutes. In order to measure energy, the unit requires voltage and current inputs in addition to the supply required to power the product.
• SDM630-Modbus V2 supports max. 80A direct connection, saves the cost and avoid the trouble to connect external CTs, giving the unit a cost-effective and easy operation. Built-in interfaces provide pulse and RS485 Modbus RTU outputs. Configuration is password protected.

Unit Characteristics

• The Unit can measure and display:
  • Line voltage and THD% (total harmonic distortion) of all phases
  • Line Frequency
  • Currents, Current demands and current THD% of all phases
  • Power, maximum power demand and power factor
  • Active energy imported and exported
  • Reactive energy imported and exported
• The unit has password-protected set-up screens for:
  • Changing password
  • Supply system selection 1p2w, 3p3w,3p4w
  • Demand Interval Time (DIT)
  • Reset for demand measurements
  • Pulse output duration

Two pulse outputs indicate real-time energy measurement. An RS485 output allows remote monitoring from another display or a computer.

RS485 Serial–Modbus RTU

• This uses an RS485 serial port with Modbus RTU protocol to provide a means of remotely monitoring and controlling the Unit.
• Set-up screens are provided for setting up the RS485 port.

Pulse Output

• This provides two pulse outputs that clock up measured active and reactive energy. The constant of pulse output 2 for only import active energy is 400imp/kWh (unconfigurable), its width is fixed at 100ms.
• The default constant of configurable pulse output 1 is 400imp/kWh, default pulse width is 100ms. The configurable pulse output 1 can be set from the set-up menu.

Start-up Screens

1| | The first screen lights up all display segments and can be used as a display check.
---|---|---
2| | The second screen indicates the firmware installed in the unit and its build number.

*The build number (1.302.2019) is for reference only. The actual build number changes according to product requirements.

3| | The interface performs a self-test and indicates the result if the test passes.

After a short delay, the screen will display active energy measurements.

Measurements
The buttons operate as follows:

1| | Selects the Voltage and Current display screens
In Set-up Mode, this is the “Left” or “Back” button.
---|---|---
2| | Select the Frequency and Power factor display screens
In Set-up Mode, this is the “Up” button
3| | Select the Power display screens
In Set-up Mode, this is the “Down” button
4| | Select the Energy display screens
In Set-up mode, this is the “Enter” or “Right” button

Voltage and Current

Each successive pressing of the   button selects a new range:

Frequency and Power Factor and Demand
Each successive pressing of the button selects a new range: Power
Each successive pressing of the button select a new range: Energy Measurements
Each successive pressing of the button selects a new range: Set-up

• To enter set-up mode, pressing the button for 3 seconds, until the password screen appears.
• Setting up is password-protected so you must enter the correct password (default ‘1000’) before processing.
• If an incorrect password is entered, the display will show: PASS Err
• To exit setting-up mode, press repeatedly until the measurement screen is restored.

Set-up Entry Methods
Some menu items, such as password, require a four-digit number entry while others, such as supply system, require selection from a number of menu options.

Menu Option Selection

1. Use the and buttons to select the required item from the menu. Selection does not roll over between bottom and top of list.
2. Press to confirm your selection.
3. If an item flashes, then it can be adjusted by the and buttons. If not, there maybe a further layer.
4. Having selected an option from the current layer, press to confirm your selection. The SET indicator will appear.
5. Having completed a parameter setting, press to return to a higher menu level. The SET indicator will be removed and you will be able to use the and buttons for further menu selection.
6. On completion of all set-up, press repeatedly until the measurement screen is restored.

Number Entry Procedure
When setting up the unit, some screens require the entering of a number. In particular, on entry to the setting up section, a password must be entered. Digits are set individually, from left to right. The procedure is as follows:

1. The current digit to be set flashes and is set using the and buttons.
2. Press to confirm each digit setting. The SET indicator appears after the last digit has been set.
3. After setting the last digit, press to exit the number setting routine.

Change Password

• DIT Demand Integration Time
  This sets the period in minutes over which the current and power readings are integrated for maximum demand measurement. The options are: 0, 5, 8, 10, 15, 20, 30, 60 minutes

• Backlit Set-up

• Supply System
  Use this section to set the type of electrical system.

Pulse Output
This option allows you to configure the pulse output 1. The output can be set to provide a pulse for a defined amount of energy active or reactive.

Use this section to set up the pulse output for:

• Total kWh/ Total kVArh
• Import kWh/Export kWh
• Import KVArh/Export KVArh

Pulse Rate
Use this to set the energy represented by each pulse. Rate can be set to 1 pulse per dFt/0.01/0.1/1/10/100kWh/kVArh.

Pulse Duration
The energy monitored can be active or reactive and the pulse width can be selected as 200, 100(default) or 60ms.

Communication
There is a RS485 port can be used for communication using Modbus RTU protocol. For Modbus RTU, parameters are selected from Front panel.

RS485 Address

Baud Rate

Parity Stop Bits

• to the main set up menu.
• Note: Default is 1, and only when the parity is NONE that the stop bit can be changed to 2.

CLR
The meter provides a function to reset the maximum demand value of current and power.

Specifications

• Measured Parameters
  The unit can monitor and display the following parameters of a single phase two wire(1p2w), three phase three wire(3p3w) or four phase four wire(3p4w) supply.

• Voltage and Current

  • Phase to neutral voltages 100 to 289V a.c. (not for 3p3w supplies)
  • Voltages between phases 173 to 500V a.c. (3p supplies only)
  • Percentage total voltage harmonic distortion (THD%) for each phase to N ( not for 3p3w supplies)
  • Percentage voltage THD% between phases (three phase supplies only)
  • Current THD% for each phase

• Power Factor and Frequency and Max. Demand

  • Frequency in Hz

• Instantaneous power:

  • Power 0 to 99999W
  • Reactive Power 0 to 99999 VAr
  • Volt-amps 0 to 99999 VA
  • Maximum demanded power since last Demand reset Power factor
  • Maximum neutral demand current, since the last Demand reset (for 3p4w supply only)

• Energy Measurements

  • Imported active energy 0 to 999999.99 kWh
  • Exported active energy 0 to 999999.99 kWh
  • Imported reactive energy 0 to 999999.99 kVArh
  • Exported reactive energy 0 to 999999.99 kVArh
  • Total active energy 0 to 999999.99 kWh
  • Total reactive energy 0 to 999999.99 kVArh

• Measured Inputs

  • Voltage inputs through 4-way fixed connector with 25mm² stranded wire capacity. single phase two wire(1p2w), three phase three wire(3p3w) or four phase four wire(3p4w) unbalanced. Line frequency measured from L1 voltage or L3 voltage.

• Accuracy

  • Voltage 0·5% of range maximum
  • Current 0·5% of nominal
  • Frequency 0·2% of mid-frequency
  • Power factor 1% of unity (0.01)
  • Active power (W) ±1% of range maximum
  • Reactive power (VAr) ±1% of range maximum
  • Apparent power (VA) ±1% of range maximum
  • Active energy (Wh)
  • Class 1 IEC 62053-21
  • Class B EN50470-1/3
  • Reactive energy (VArh) Class 2 IEC 62053-23
  • Response time to step input 1s, typical, to >99% of final reading, at 50 Hz.

Interfaces for External Monitoring

• Three interfaces are provided:
  • RS485 communication channel that via protocol remotely.
  • Pulse output(Pulse 1) indicating real-time measured energy.(configurable)
  • an Pulse output(Pulse 2) 400imp/kWh(non-configurable)
• The Modbus configuration (Baud rate etc.) and the pulse output assignments (kW/kVArh, import/export etc.) are configured through the Set-up screens.

Pulse Output

• The unit provides two pulse outputs. Both pulse outputs are passive type.
• Pulse output 1 is configurable. The pulse output can be set to generate pulses to represent total / import or export for kWh or kVarh.
• The pulse constant can be set to generate 1 pulse per:
  • dFt = 2.5 Wh/VArh
  • 0.01 = 10Wh/VArh
  • 0.1 = 100Wh/VArh
  • 1 = 1 kWh/kVArh
  • 10 = 10 kWh/kVArh
  • 100 = 100 kWh/kVArh
  • Pulse width: 200/100/60ms
• Pulse output 2 is non-configurable. It is fixed up with active import kWh. The constant is 400imp/kWh.
• As a hint, the meter can provide both S0 pulse output at the same time. For example you can use pulse output 1 for export active energy and pulse output two tor import active energy.

RS485 Output for Modbus RTU

• For Modbus RTU, the following RS485 communication parameters can be configured from the Set-up menu:
  • Baud rate 2400, 4800, 9600, 19200, 38400
  • Parity none (default)/odd/even
  • Stop bits 1 or 2
• RS485 network address nnn – 3-digit number, 001 to 247
• Modbus™ Word order Hi/Lo byte order is set automatically to normal or reverse. It cannot be configured from the set-up menu.

Reference Conditions of Influence Quantities
Influence Quantities are variables that affect measurement errors to a minor degree. Accuracy is verified under nominal value (within the specified tolerance) of these conditions.

• Ambient temperature 23°C ±1°C
• Input frequency 50Hz(MID)
  • 50 or 60Hz ±2%(non-MID)
• Input waveform Sinusoidal (distortion factor < 0·005)
• Magnetic field of external origin Terrestrial flux

Environment

• Operating temperature 3K6(-25°C to +55°C),Default 3K7(-40°C to +70°C)

• Storage temperature -40°C to +70°C*

• Relative humidity 0 to 90%, non-condensing

• Altitude Up to 2000m

• Warm up time 5S

• Vibration 10Hz to 50Hz, IEC 60068-2-6, 2g

• Shock 30g in 3 planes

• Maximum operating and storage temperatures are in the context of typical daily and seasonal variation.

Dimensions

Wiring Guide

Wiring diagram

• Three Phase ThreeWires
• Three Phase FourWires
• Single Phase two Wires

Zhejiang Eastron Electronic Co., Ltd. / Jiaxing PRC

• If you have any question, please feel free to contact our German sales team.
• B+G e-tech GmbH • Franz-Mehring-Str. 36 • DE 01979 Lauchhammer
• Telefon / WhatsApp: +49 3574 467550 • Fax: +49 3574 467550
• Web: www.eastron-germany.de • E-Mail: post@eastron-germany.de

Eastron SDM630Modbus Smart Meter Modbus Protocol Implementation V1.6B

Modbus Protocol Overview

• This section provides basic information for interfacing the Eastron Smart meter to a Modbus Protocol network. If background information or more details of the Eastron implementation is required please refer to section 2 and 3 of this document.
• Eastron offers the option of an RS485 communication facility for direct connection to SCADA or other communications systems using the Modbus Protocol RTU salve protocol. The Modbus Protocol establishes the format for the master’s query by placing into it the device address, a function code defining the requested action, any data to be sent, and an error checking field. The slave’s response message is also constructed using Modbus Protocol. It contains fields confirming the action taken, any data to be returned, and an error-checking field. If an error occurs in receipt of the message, SDM630Modbus will make no response. If the SDM630Modbus is unable to perform the requested action, it will construct an error message and send it as the response.
• The electrical interface is 2-wire RS485, via 2 screw terminals. Connection should be made using twisted pair screened cable (Typically 22 gauge Belden 8761 or equivalent). All “A” and “B” connections are daisy chained together. Line topology may or may not require terminating loads depending on the type and length of cable used. Loop (ring) topology does not require any termination load. The impedance of the termination load should match the impedance of the cable and be at both ends of the line. The cable should be terminated at each end with a 120 ohm (0.25 Watt min.) resistor. A total maximum length of 3900 feet (1200 meters) is allowed for the RS485 network. A maximum of 32 electrical nodes can be connected, including the controller. The address of each Eastron can be set to any value between 1 and 247. Broadcast mode (address 0) is supported.

The format for each byte in RTU mode is:

• Coding System: 8-bit per byte
• Data Forma t: 4 bytes (2 registers) per parameter.
  • Floating point format ( to IEEE 754)
  • Most significant register first (Default). The default may be changed if required -See Holding Register
  • “Register Order” parameter.
• Error Check Field : 2 byte Cyclical Redundancy Check (CRC)
• Framing: 1 start bit
  • 8 data bits, least significant bit sent first
  • 1 bit for even/odd parity (or no parity)
  • 1 stop bit if parity is used; 1 or 2 bits if no parity

Data Coding

• All data values in the SDM630Modbus smart meter are transferred as 32 bit IEEE754 floating point numbers, (input and output) therefore each SDM630Modbus meter value is transferred using two Modbus Protocol registers. All register read requests and data write requests must specify an even number of registers. Attempts to read/write an odd number of registers prompt the SDM630Modbus smart meter to return a Modbus Protocol exception message. However, for compatibility with some SCADA systems, SDM630Modbus Smart meter will response to any single input or holding register read with an instrument type specific value.
• The SDM630Modbus can transfer a maximum of 40 values in a single transaction; therefore the maximum number of registers requestable is 80. Exceeding this limit prompts the SDM630Modbus to generate an exception response.
• Data transmission speed is selectable between 2400, 4800, 9600, 19200, 38400, 115200 baud.

Input register

• Input registers are used to indicate the present values of the measured and calculated electrical quantities. Each parameter is held in two consecutive16 bit register.The following table details the 3X register address, and the values of the address bytes within the message. A (*) in the column indicates that the parameter is valid for the particular wiring system. Any parameter with a cross(X) will return the value zero. Each parameter is held in the 3X registers. Modbus Protocol function code 04 is used to access all parameters.

• For example, to request:

  • Amps 1 Start address=0006
    No. of registers =0002

  • Amps 2 Start address=0008
    No. of registers=0002

• Each request for data must be restricted to 40 parameters or less. Exceeding the 40 parameter limit will cause a Modbus Protocol exception code to be returned.

SDM630Modbus Input Registers

Address| Parameter| SDM630Modbus Input Register Parameter| Modbus Protocol Start Address Hex| ****

3

Ø

| ****

3

Ø

| ****

1

Ø

---|---|---|---|---|---|---
(Register)| Number| Description| Units| Hi

Byte

| Lo

Byte

| 4

W

| 3

W

| 2

W

30001| 1| Phase 1 line to neutral volts.| Volts| 00| 00 √| X √| |
30003| 2| Phase 2 line to neutral volts.| Volts| 00| 02 √| X| X|
30005| 3| Phase 3 line to neutral volts.| Volts| 00| 04 √| X| X|
30007| 4| Phase 1 current.| Amps| 00| 06 √ √ √| | |
30009| 5| Phase 2 current.| Amps| 00| 08 √ √| X| |
30011| 6| Phase 3 current.| Amps| 00| 0A √ √| X| |
30013| 7| Phase 1 power.| Watts| 00| 0C √| X √| |
30015| 8| Phase 2 power.| Watts| 00| 0E √| X √| |
30017| 9| Phase 3 power.| Watts| 00| 10 √| X| X|
30019| 10| Phase 1 volt amps.| VA| 00| 12 √| X √| |
30021| 11| Phase 2 volt amps.| VA| 00| 14 √| X| X|
30023| 12| Phase 3 volt amps.| VA| 00| 16 √| X| X|
30025| 13| Phase 1 volt amps reactive.| VAr| 00| 18 √| X √| |
30027| 14| Phase 2 volt amps reactive.| VAr| 00| 1A √| X| X|
30029| 15| Phase 3 volt amps reactive.| VAr| 00| 1C √| X| X|
30031| 16| Phase 1 power factor (1).| None| 00| 1E √| X √| |
30033| 17| Phase 2 power factor (1).| None| 00| 20 √| X| X|
30035| 18| Phase 3 power factor (1).| None| 00| 22 √| X| X|
30037| 19| Phase 1 phase angle.| Degree| 00| 24 √| X √| |
| | | s| | | | |
---|---|---|---|---|---|---|---|---
30039| 20| Phase 2 phase angle.| Degrees| 00| 26 √| X| X|
30041| 21| Phase 3 phase angle.| Degrees| 00| 28 √| X| X|
30043| 22| Average line to neutral volts.| Volts| 00| 2A √| X| X|
30047| 24| Average line current.| Amps| 00| 2E √ √ √| | |
30049| 25| Sum of line currents.| Amps| 00| 30 √ √ √| | |
30053| 27| Total system power.| Watts| 00| 34 √ √ √| | |
30057| 29| Total system volt amps.| VA| 00| 38 √ √ √| | |
30061| 31| Total system VAr.| VAr| 00| 3C √ √ √| | |
30063| 32| Total system power factor (1).| None| 00| 3E √ √ √| | |
30067| 34| Total system phase angle.| Degree

s

| 00| 42 √ √ √| | |
30071| 36| Frequency of supply voltages.| Hz| 00| 46 √ √ √| | |
30073| 37| Import Wh since last reset (2).| kWh/

MWh

| 00| 48 √ √ √| | |
30075| 38| Export Wh since last reset (2).| kWh/

MWh

| 00| 4A √ √ √| | |
30077| 39| Import VArh since last reset (2).| kVArh/

MVArh

| 00| 4C √ √ √| | |
30079| 40| Export VArh since last reset (2).| kVArh/

MVArh

| 00| 4E √ √ √| | |
30081| 41| VAh since last reset (2).| kVAh/

MVAh

| 00| 50 √ √ √| | |
30083| 42| Ah since last reset(3).| Ah/kAh| 00| 52 √ √ √| | |
30085| 43| Total system power demand (4).| W| 00| 54 √ √ √| | |
30087| 44| Maximum total system power demand (4).| VA| 00| 56 √ √ √| | |
30101| 51| Total system VA demand.| VA| 00| 64 √ √ √| | |
30103| 52| Maximum     total    system     VA

demand.

| VA| 00| 66 √ √ √| | |
30105| 53| Neutral current demand.| Amps| 00| 68 √| X| X|
30107| 54| Maximum        neutral       current

demand.

| Amps| 00| 6A √| X| X|
30201| 101| Line 1 to Line 2 volts.| Volts| 00| C8 √ √| X| |
30203| 102| Line 2 to Line 3 volts.| Volts| 00| CA √ √| X| |
30205| 103| Line 3 to Line 1 volts.| Volts| 00| CC √ √| X| |
30207| 104| Average line to line volts.| Volts| 00| CE √ √| X| |
30225| 113| Neutral current.| Amps| 00| E0 √| X| X|
30235| 118| Phase 1 L/N volts THD| %| 00| EA √| X √| |
30237| 119| Phase 2 L/N volts THD| %| 00| EC √| X| X|
---|---|---|---|---|---|---|---|---
30239| 120| Phase 3 L/N volts THD| %| 00| EE √| X| X|
30241| 121| Phase 1 Current THD| %| 00| F0 √ √ √| | |
30243| 122| Phase 2 Current THD| %| 00| F2 √ √| X| |
30245| 123| Phase 3 Current THD| %| 00| F4 √ √| X| |
30249| 125| Average line to neutral volts THD.| %| 00| F8 √| X √| |
30251| 126| Average line current THD.| %| 00| FA √ √ √| | |
30255| 128| Total system power factor (5).| Degree| 00| FE √ √ √| | |
30259| 130| Phase 1 current demand.| Amps| 01| 02 √ √ √| | |
30261| 131| Phase 2 current demand.| Amps| 01| 04 √ √| X| |
30263| 132| Phase 3 current demand.| Amps| 01| 06 √ √| X| |
30265| 133| Maximum     phase    1     current

demand.

| Amps| 01| 08 √ √ √| | |
30267| 134| Maximum     phase    2     current

demand.

| Amps| 01| 0A √ √| X| |
30269| 135| Maximum     phase    3     current

demand.

| Amps| 01| 0C √ √| X| |
30335| 168| Line 1 to line 2 volts THD.| | 01| 4E √ √| X| |
30337| 169| Line 2 to line 3 volts THD.| | 01| 50 √ √| X| |
30339| 170| Line 3 to line 1 volts THD.| | 01| 52 √ √| X| |
30341| 171| Average line to line volts THD.| | 01| 54 √ √| X| |
30343| 172| Total kwh (Import+Export)| kwh| 01| 56 √ √ √| | |
30345| 173| Total kvarh (Import+Export)| kvarh| 01| 58 √ √ √| | |
30347| 174| L1 import kwh| kwh| 01| 5a √ √ √| | |
30349| 175| L2 import kwh| kwh| 01| 5c √ √ √| | |
30351| 176| L3 import kWh| kwh| 01| 5e √ √ √| | |
30353| 177| L1 export kWh| kwh| 01| 60 √ √ √| | |
30355| 178| L2 export kwh| kwh| 01| 62 √ √ √| | |
30357| 179| L3 export kWh| kwh| 01| 64 √ √ √| | |
30359| 180| L1 total kwh| kwh| 01| 66 √ √ √| | |
30361| 181| L2 total kWh| kwh| 01| 68 √ √ √| | |
30363| 182| L3 total kwh| kwh| 01| 6a √ √ √| | |
30365| 183| L1 import kvarh| kvarh| 01| 6c √ √ √| | |
30367| 184| L2 import kvarh| kvarh| 01| 6e √ √ √| | |
30369| 185| L3 import kvarh| kvarh| 01| 70 √ √ √| | |
30371| 186| L1 export kvarh| kvarh| 01| 72 √ √ √| | |
30373| 187| L2 export kvarh| kvarh| 01| 74 √ √ √| | |
30375| 188| L3 export kvarh| kvarh| 01| 76 √ √ √| | |
30377| 189| L1 total kvarh| kvarh| 01| 78 √ √ √| | |
30379| 190| L2 total kvarh| kvarh| 01| 7a √ √ √| | |
30381| 191| L3 total kvarh| kvarh| 01| 7c √ √ √| | |
30397| 192| Net kWh (Import-Export)| kWh| 01| 8c √ √ √| | |
---|---|---|---|---|---|---|---|---
30399| 193| Net kVArh (Import-Export)| kvarh| 01| 8e √ √ √| | |

Notes:

1. The power factor has its sign adjusted to indicate the nature of the load. Positive for capacitive and negative for inductive.
2. There is a user option to select either k or M for the energy prefix.
3. The same user option as in 2 above gives a prefix of none or k for Amp hours
4. The power sum demand calculation is for import power only
5. The negative total system power factor is a sign inverted version of parameter 32, the magnitude is the same as parameter 32.
6. There is a user option to select None, k or M for the energy prefix.

Modbus Protocol Holding Registers and Digital meter set up
Holding registers are used to store and display instrument configuration settings. All holding registers not listed in the table below should be considered as reserved for manufacturer use and no attempt should be made to modify their values.
The holding register parameters may be viewed or changed using the Modbus Protocol. Each parameter is held in two consecutive 4X registers. Modbus Protocol Function Code 03 is used to read the parameter and Function Code 16 is used to write. Write to only one parameter per message.

SDM630Modbus MODBUS Protocol Holding Register Parameters

Address Register| Parameter Number| Paramet er| Modbus Protocol Start Address Hex| Valid range| Mode
---|---|---|---|---|---
High Byte| Low Byte
40003| 2| Demand Period| 00| 02| Write demand period: 0, 5,8, 10, 15, 20, 30 or 60 minutes, default 60. Setting the period to 0 will cause the demand to show the current parameter value, and demand max to show the maximum parameter value since last demand reset.
Length : 4 byte Data Format : Float| r/w
40007| 4| System Volts| 00| 06| system voltage
Length : 4 byte Data Format : Float| R
40009| 5| System Current| 00| 08| system current
Length : 4 byte Data Format : Float| R
40011| 6| System Type| 00| 0A| Write system type: 3p4w = 3, 3p3w = 2 & 1p2w= 1
Requires password, see parameter 13
Length : 4 byte Data Format : Float| r/wp
---|---|---|---|---|---|---
40013| 7| Pulse1 Width| 00| OC| Write pulse1 on period in milliseconds: 60, 100 or 200, default 100.

Length : 4 byte Data Format : Float

| r/w
40015| 8| Password Lock| 00| OE| Write any value to password lock protected registers.
Read password lock status: 0 = locked. 1 = unlocked.
Reading will also reset the password timeout back to one minute.
Length : 4 byte Data Format : Float| r
40019| 10| Network Parity Stop| 00| 12| Write the network port parity/stop bits for MODBUS Protocol, where: 0 = One stop bit and no parity, default. 1 = One stop bit and even parity. 2 = One stop bit and odd parity.3 = Two stop bits and no parity.Requires a restart to become effective.
Length : 4 byte Data Format : Float| r/w
40021| 11| Network Node| 00| 14| Write the network port node address: 1 to 247 for MODBUS Protocol, default 1. Requires a restart to become effective.
Length : 4 byte Data Format : Float| r/w
40023| 12| Pulse1 Divisor1| 00| 16| Write pulse divisor index:

• n = 0 to 5
• 0–0.0025 kWh(kVArh)/imp
• 1–0.01 kWh(kVArh)/imp
• 2–0.1 kWh(kVArh)/imp
• 3—1 kWh(kVArh)/imp
• 4-10 kWh(kVArh)/imp
• 5-100 kWh(kVArh)/imp

Length : 4 byte Data Format : Float

| r/w
40025| 13| Password| 00| 18| Write password for access to protected registers.
Length : 4 byte Data Format : Float| r/w
---|---|---|---|---|---|---
40029| 15| Network Baud Rate| 00| 1C| Write the network port baud rate for MODBUS Protocol, where:

• 0 = 2400 baud. 1 = 4800 baud.
• 2 = 9600 baud, default.
• 3 = 19200 baud.
• 4 = 38400 baud.
• 5 = 115200 baud Requires a restart to become effective

Length : 4 byte Data Format : Float

| r/w
40037| 19| System Power| 00| 24| Read the total system power, e.g. for 3p4w returns System Volts x System Amps x 3.

Length : 4 byte Data Format : Float

| r
40087| 44| Pulse 1 Energy Type| 00| 56| Write MODBUS Protocol input parameter for pulse output 1:

• 1: import active energy
• 2: total active energy
• 4: export active energy, default
• 5: import reactive energy
• 6: total reactive energy
• 8: export reactive energy

Length : 4 byte Data Format : Float

| r/w

Register Order controls the order in which the Eastron Digital meter receives or sends floating-point numbers:

• normal or reversed register order. In normal mode, the two registers that make up a floating point number are sent most significant register first. In reversed register mode, the two registers that make up a floating point number are sent least significant register first. To set the mode, write the value ‘2141.0’ into this register – the instrument will detect the order used to send this value and set that order for all Modbus Protocol transactions involving floating point numbers.
• It is perfectly feasible to change Eastron Digital meter set-up using a general purpose Modbus Protocol master, but often easier to use the Eastron Digital meter display or Eastron Digital meter configurator software, especially for gaining password protected access. The Eastron Digital meter configurator software has facilities to store configurations to disk for later retrieval and rapid set up of similarly configured products.

Password

• Some of the parameters described above are password protected and thus require the password to be entered at the Password register before they can be changed. The default password is 0000. When the password has been entered it will timeout in one minute unless the Password or Password Lock register is read to reset the timeout timer. Once the required changes have been made to the protected parameters the password lock should be reapplied by
  • allowing the password to timeout, or
  • writing any value to the Password Lock register, or
  • power cycling the instrument.

2 RS485 General Information

Some of the information in this section relates to other Eastron Digital meter product families, and is included to assist where a mixed network is implemented.RS485 or EIA (Electronic Industries Association) RS485 is a balanced line, half-duplex transmission system allowing transmission distances of up to 1.2 km. The following table summarizes the RS-485 Standard:

PARAMETER|
---|---
Mode of Operation| Differential
Number of Drivers and Receivers| 32 Drivers, 32 Receivers
Maximum Cable Length| 1200 m
Maximum Data Rate| 10 M baud
Maximum Common Mode Voltage| 12 V to –7 V
Minimum Driver Output Levels (Loaded)| +/– 1.5 V
Minimum Driver Output Levels (Unloaded)| +/– 6 V
Drive Load| Minimum 60 ohms
Driver Output Short Circuit Current Limit| 150 mA to Gnd, 250 mA to 12 V 250 mA to –7 V
Minimum Receiver Input Resistance| 12 kohms
Receiver Sensitivity| +/– 200 mV

Further information relating to RS485 may be obtained from either the EIA or the various RS485 device manufacturers, for example Texas Instruments or Maxim Semiconductors. This list is not exhaustive.

Half Duplex

• Half duplex is a system in which one or more transmitters (talkers) can communicate with one or more receivers (listeners) with only one transmitter being active at any one time. For example, a “conversation” is started by asking a question, the person who has asked the question will then listen until he gets an answer or until he decides that the individual who was asked the question is not going to reply.
• In a 485 network the “master” will start the “conversation” with a “query” addressed to a specific “slave”, the “master” will then listen for the “slave’s” response. If the “slave” does not respond within a pre-defined period, (set by control software in the “master”), the “master” will abandon the “conversation”.

Connecting the Instruments

• If connecting an RS485 network to a PC use caution if contemplating the use of an RS232 to 485 converter together with a USB to RS485 adapter. Consider either an RS232 to RS485 converter, connected directly to a suitable RS232 jack on the PC, or use a USB to RS485 converter or, for desktop PCs a suitable plug in RS485 card. (Many 232:485 converters draw power from the RS232 socket. If using a USB to RS232 adapter, the adapter may not have enough power available to run the 232:485 converter.)
• Screened twisted pair cable should be used. For longer cable runs or noisier environments, use of a cable specifically designed for RS485 may be necessary to achieve optimum performance. All “A” terminals should be connected together using one conductor of the twisted pair cable, all “B” terminals should be connected together using the other conductor in the pair. The cable screen should be connected to the “Gnd” terminals.
• A Belden 9841 (Single pair) or 9842 (Two pair) or similar cable with a characteristic impedance of 120 ohms is recommended. The cable should be terminated at each end with a 120 ohm, quarter watt (or greater) resistor. Note: Diagram shows wiring topology only. Always follow terminal identification on Eastron Digital meter product label.
• There must be no more than two wires connected to each terminal, this ensures that a “Daisy Chain or “straight line” configuration is used.
• A “Star” or a network with “Stubs (Tees)” is not recommended as reflections within the cable may result in data corruption.

A and B terminals
The A and B connections to the Eastron Digital meter products can be identified by the signals present on them whilst there is activity on the RS485 bus:

Troubleshooting

• Start with a simple network, one master and one slave. With Eastron Digital meter products this is easily achieved as the network can be left intact whilst individual instruments are disconnected by removing the RS485 connection from the rear of the instrument.
• Check that the network is connected together correctly. That is all of the “A’s” are connected together, and all of the “B’s” are connected together, and also that all of the “Gnd’s” are connected together.
• Confirm that the data “transmitted” onto the RS485 is not echoed back to the PC on the RS232 lines.(This facility is sometimes a link option within the converter). Many PC based packages seem to not perform well when they receive an echo of the message they are transmitting. SpecView and PCView (PC software) with a RS232 to RS485 converter are believed to include this feature.
• Confirm that the Address of the instrument is the same as the “master” is expecting.
• If the “network” operates with one instrument but not more than one check that each instrument has a unique address.
• Each request for data must be restricted to 40 parameters or less. Violating this requirement will impact the performance of the instrument and may result in a response time in excess of the specification.
• Check that the MODBUS Protocol mode (RTU or ASCII) and serial parameters (baud rate, number of data bits, number of stop bits and parity) are the same for all devices on the network.
• Check that the “master” is requesting floating-point variables (pairs of registers placed on floating point boundaries) and is not “splitting” floating point variables.
• Check that the floating-point byte order expected by the “master” is the same as that used by Eastron Digital meter products. (PCView and Citect packages can use a number of formats including that supported by Eastron Digital meter).
• If possible obtain a second RS232 to RS485 converter and connect it between the RS485 bus and an additional PC equipped with a software package, which can display the data on the bus. Check for the existence of valid requests.

3 MODBUS Protocol General Information

• Communication on a MODBUS Protocol Network is initiated (started) by a “Master” sending a query to a “Slave”. The “Slave“, which is constantly monitoring the network for queries addressed to it, will respond by performing the requested action and sending a response back to the ”Master”. Only the “Master” can initiate a query.
  

• In the MODBUS Protocol the master can address individual slaves, or, using a special “Broadcast” address, can initiate a broadcast message to all slaves. The Eastron Digital meter do not support the broadcast address.

MODBUS Protocol Message Format

• The MODBUS Protocol defines the format for the master’s query and the slave’s response.
• The query contains the device (or broadcast) address, a function code defining the requested action, any data to be sent, and an error-checking field.
• The response contains fields confirming the action taken, any data to be returned, and an error-checking field. If an error occurred in receipt of the message then the message is ignored, if the slave is unable to perform the requested action, then it will construct an error message and send it as its response. The MODBUS Protocol functions used by the Eastron Digital meters copy 16 bit register values between master and slaves. However, the data used by the Eastron Digital meter is in 32 bit IEEE 754 floating point format. Thus each instrument parameter is conceptually held in two adjacent MODBUS Protocol registers. Query
• The following example illustrates a request for a single floating point parameter i.e. two 16-bit Modbus Protocol Registers.

First Byte Last Byte

Slave Address| Function Code| Start Address (Hi)| Start Address (Lo)| Number of Points (Hi)| Number of Points (Lo)| Number of Points (Lo)| Error Check (Lo)| Error Check (Hi)
---|---|---|---|---|---|---|---|---

• Slave Address: 8-bit value representing the slave being addressed (1 to 247), 0 is reserved for the broadcast address. The Eastron Digital meters do not support the broadcast address.
• Function Code: 8-bit value telling the addressed slave what action is to be performed. (3, 4, 8 or 16 are valid for Eastron Digital meter)
• Start Address (Hi): The top (most significant) eight bits of a 16-bit number specifying the start address of the data being requested.
• Start Address (Lo): The bottom (least significant) eight bits of a 16-bit number specifying the start address of the data being requested. As registers are used in pairs and start at zero, then this must be an even number.
• Number of Points (Hi): The top (most significant) eight bits of a 16-bit number specifying the number of registers being requested.
• Number of Points (Lo): The bottom (least significant) eight bits of a 16-bit number specifying the number of registers being requested. As registers are used in pairs, then this must be an even number.
• Error Check (Lo): The bottom (least significant) eight bits of a 16-bit number representing the error check value.
• Error Check (Hi): The top (most significant) eight bits of a 16-bit number representing the error check value.

Response
The example illustrates the normal response to a request for a single floating point parameter i.e. two 16-bit Modbus Protocol Registers.
First Byte

Slave Address| Function Code| Byte Count| First Register (Hi)| First Register (Lo)| Second Register (Hi)| Second Register (Lo)| Error Check (Lo)| Error Check (Hi)
---|---|---|---|---|---|---|---|---

• Slave Address: 8-bit value representing the address of slave that is responding.
• Function Code: 8-bit value which, when a copy of the function code in the query, indicates that the slave recognised the query and has
• responded. (See also Exception Response).
• Byte Count: 8-bit value indicating the number of data bytes contained within this response
• First Register (Hi)*: The top (most significant) eight bits of a 16-bit number representing the first register requested in the query.
• First Register (Lo)*: The bottom (least significant) eight bits of a 16-bit number representing the first register requested in the query.
• Second Register (Hi)*: The top (most significant) eight bits of a 16-bit number representing the second register requested in the query.
• Second Register (Lo)*: The bottom (least significant) eight bits of a 16-bit number representing the second register requested in the query.
• Error Check (Lo): The bottom (least significant) eight bits of a 16-bit number representing the error check value.
• Error Check (Hi): The top (most significant) eight bits of a 16-bit number representing the error check value.

*These four bytes together give the value of the floating point parameter requested.

Exception Response
If an error is detected in the content of the query (excluding parity errors and Error Check mismatch), then an error response (called an exception response), will be sent to the master. The exception response is identified by the function code being a copy of the query function code but with the most- significant bit set. The data contained in an exception response is a single byte error code.

First Byte Last Byte

• Slave Address: 8-bit value representing the address of slave that is responding.
• Function Code: 8 bit value which is the function code in the query OR’ed with 80 hex, indicating that the slave either does not recognise the query or could not carry out the action requested.
• Error Code: 8-bit value indicating the nature of the exception detected. (See “Table Of Exception Codes“ later).
• Error Check (Lo): The bottom (least significant) eight bits of a 16-bit number representing the error check value.
• Error Check (Hi): The top (most significant) eight bits of a 16-bit number representing the error check value.

Serial Transmission Modes

• There are two MODBUS Protocol serial transmission modes, ASCII and RTU. Eastron Digital meters do not support the ASCII mode.
• In RTU (Remote Terminal Unit) mode, each 8-bit byte is used in the full binary range and is not limited to ASCII characters as in ASCII Mode. The greater data density allows better data throughput for the same baud rate, however each message must be transmitted in a continuous stream. This is very unlikely to be a problem for modern communications equipment.
• Coding System: Full 8-bit binary per byte. In this document, the value of each byte will be shown as two hexadecimal characters each in the range 0-9 or A-F.
• Line Protocol: 1 start bit, followed by the 8 data bits. The 8 data bits are sent with least significant bit first.
• User Option Of Parity No Parity and 2 Stop Bits
• And Stop Bits: No Parity and 1 Stop Bit
• Even Parity and 1 Stop Bit
• Odd Parity and 1 Stop Bit.
• User Option of Baud 2400; 4800 ; 9600 ; 19200 ; 38400
• The baud rate, parity and stop bits must be selected to match the master’s settings.

MODBUS Protocol Message Timing (RTU Mode)

• A MODBUS Protocol message has defined beginning and ending points. The receiving devices recognizes the start of the message, reads the “Slave Address” to determine if they are being addressed and knowing when the message is completed they can use the Error Check bytes and parity bits to confirm the integrity of the message. If the Error Check or parity fails then the message is discarded.
• In RTU mode, messages starts with a silent interval of at least 3.5 character times.
• The first byte of a message is then transmitted, the device address.
• Master and slave devices monitor the network continuously, including during the ‘silent’ intervals.When the first byte (the address byte) is received, each device checks it to find out if it is the addressed device. If the device determines that it is the one being addressed it records the whole message and acts accordingly, if it is not being addressed it continues monitoring for the next message.
• Following the last transmitted byte, a silent interval of at least 3.5 character times marks the end of the message. A new message can begin after this interval.
• In the Eastron 1000 and 2000, a silent interval of 60msec minimum is required in order to guarantee successful reception of the next request.
• The entire message must be transmitted as a continuous stream. If a silent interval of more than 1.5 character times occurs before completion of the message, the receiving device flushes the incomplete message and assumes that the next byte will be the address byte of a new message.
• Similarly, if a new message begins earlier than 3.5 character times following a previous message, the receiving device may consider it a continuation of the previous message. This will result in an error, as the value in the final CRC field will not be valid for the combined messages.

How Characters are Transmitted Serially
When messages are transmitted on standard MODBUS Protocol serial networks each byte is sent in this order (left to right):

• Transmit Character = Start Bit + Data Byte + Parity Bit + 1 Stop Bit (11 bits total):
• The master is configured by the user to wait for a predetermined timeout interval. The master will wait for this period of time before deciding that the slave is not going to respond and that the transaction should be aborted. Care must be taken when determining the timeout period from both the master and the slaves’ specifications. The slave may define the ‘response time’ as being the period from the receipt of the last bit of the query to the transmission of the first bit of the response. The master may define the ‘response time’ as period between transmitting the first bit of the query to the receipt of the last bit of the response. It can be seen that message transmission time, which is a function of the baud rate, must be included in the timeout calculation.

Error Checking Methods
Standard MODBUS Protocol serial networks use two error checking processes, the error check bytes mentioned above check message integrity whilst Parity checking (even or odd) can be applied to each byte in the message.

1. Parity Checking
   If parity checking is enabled – by selecting either Even or Odd Parity – the quantity of “1’s” will be counted in the data portion of each transmit character. The parity bit will then be set to a 0 or 1 to result in an Even or Odd total of “1’s”.
   Note that parity checking can only detect an error if an odd number of bits are picked up or dropped in a transmit character during transmission, if for example two 1’s are corrupted to 0’s the parity check will not find the error.
   If No Parity checking is specified, no parity bit is transmitted and no parity check can be made. Also, if No Parity checking is specified and one stop bit is selected the transmit character is effectively shortened by one bit.

2. CRC Checking

   • The error check bytes of the MODBUS Protocol messages contain a Cyclical Redundancy Check (CRC) value that is used to check the content of the entire message. The error check bytes must always be present to comply with the MODBUS Protocol, there is no option to disable it.

   • The error check bytes represent a 16-bit binary value, calculated by the transmitting device. The receiving device must recalculate the CRC during receipt of the message and compare the calculated value to the value received in the error check bytes. If the two values are not equal, the message should be discarded.

   • The error check calculation is started by first pre-loading a 16-bit register to all 1’s (i.e. Hex (FFFF)) each successive 8-bit byte of the message is applied to the current contents of the register. Note: only the eight bits of data in each transmit character are used for generating the CRC, start bits, stop bits and the parity bit, if one is used, are not included in the error check bytes.

   • During generation of the error check bytes, each 8-bit message byte is exclusive OR’ed with the lower half of the 16 bit register. The register is then shifted eight times in the direction of the least significant bit (LSB), with a zero filled into the most significant bit (MSB) position. After each shift the LSB prior to the shift is extracted and examined. If the LSB was a 1, the register is then exclusive OR’ed with a pre-set, fixed value. If the LSB was a 0, no exclusive OR takes place.

   • This process is repeated until all eight shifts have been performed. After the last shift, the next 8-bit message byte is exclusive OR’ed with the lower half of the 16 bit register, and the process repeated. The final contents of the register, after all the bytes of the message have been applied, is the error check value. In the following pseudo code “Error Word” is a 16-bit value representing the error check values.

   • BEGIN

   • Error Word = Hex (FFFF)

   • FOR Each byte in message

   • Error Word = Error Word XOR byte in message

   • FOR Each bit in byte

   • LSB = Error Word AND Hex (0001)

   • IF LSB = 1 THEN Error Word = Error Word – 1
     Error Word = Error Word / 2

   • IF LSB = 1 THEN Error Word = Error Word XOR Hex (A001)

   • NEXT bit in byte

   • NEXT Byte in message

   • END

Function Codes
The function code part of a MODBUS Protocol message defines the action to be taken by the slave. Eastron Digital meters support the following function codes:

references)
04| Read Input Registers| Read the contents of read only location(3X references)
08| Diagnostics| Only sub-function zero is supported.
This returns the data element of the query unchanged.
15| Pre-set Multiple Registers| Set the contents of read/write location (4X references)

IEEE floating point format

• The MODBUS Protocol defines 16 bit “Registers” for the data variables. A 16-bit number would prove too restrictive, for energy parameters for example, as the maximum range of a 16-bit number is 65535.
• However, there are a number of approaches that have been adopted to overcome this restriction. Eastron Digital meters use two consecutive registers to represent a floating-point number, effectively expanding the range to +/- 1×1037.
• The values produced by Eastron Digital meters can be used directly without any requirement to “scale” the values, for example, the units for the voltage parameters are volts, the units for the power parameters are watts etc.
• What is a floating point Number?
  A floating-point number is a number with two parts, a mantissa and an exponent and is written in the form 1.234 x 105. The mantissa (1.234 in this example) must have the decimal point moved to the right with the number of places determined by the exponent (5 places in this example) i.e. 1.234x 105 =

123400. If the exponent is negative the decimal point is moved to the left.

• What is an IEEE 754 format floating-point number?
  An IEEE 754 floating point number is the binary equivalent of the decimal floating-point number shown above. The major difference being that the most significant bit of the mantissa is always arranged to be 1 and is thus not needed in the representation of the number. The process by which the most significant bit is arranged to be 1 is called normalization, the mantissa is thus referred to as a “normal mantissa”. During normalization the bits in the mantissa are shifted to the left whilst the exponent is decremented until the most significant bit of the mantissa is one. In the special case where the number is zero both mantissa and exponent are zero.

The bits in an IEEE 754 format have the following significance:

Data Hi Reg,

Hi Byte.

| Data Hi Reg,

Lo Byte.

| Data Lo Reg,

Hi Byte.

| Data Lo Reg,

Lo Byte.

---|---|---|---
SEEE

EEEE

| EMMM

MMMM

| MMMM

MMMM

| MMMM

MMMM

Where:

• S represents the sign bit where 1 is negative and 0 is positive E is the 8-bit exponent with an offset of 127 i.e. an exponent of zero is represented by 127, an exponent of 1 by 128 etc.
• M is the 23-bit normal mantissa. The 24th bit is always 1 and, therefore, is not stored.

Using the above format the floating point number 240.5 is represented as 43708000 hex:

Data Hi Reg,

Hi Byte

| Data Hi Reg,

Lo Byte

| Data Lo Reg,

Hi Byte

| Data Lo Reg,

Lo Byte

---|---|---|---
43| 70| 80| 00

• The following example demonstrates how to convert IEEE 754 floating-point numbers from their hexadecimal form to decimal form. For this example, we will use the value for 240.5 shown above
• Note that the floating-point storage representation is not an intuitive format. To convert this value to decimal, the bits should be separated as specified in the floating-point number storage format table shown above.

For example:

Data Hi Reg,

Hi Byte

| Data Hi Reg,

Lo Byte

| Data Lo Reg,

Hi Byte

| Data Lo Reg,

Lo Byte

---|---|---|---
0100 0011| 0111 0000| 1000 0000| 0000 0000

• From this you can determine the following information.

  • The sign bit is 0, indicating a positive number.
  • The exponent value is 10000110 binary or 134 decimal. Subtracting 127 from 134 leaves 7, which is the actual exponent.
  • The mantissa appears as the binary number 11100001000000000000000

• There is an implied binary point at the left of the mantissa that is always preceded by a 1. This bit is not stored in the hexadecimal representation of the floating-point number. Adding 1 and the binary point to the beginning of the mantissa gives the following:

  • 1.11100001000000000000000

• Now, we adjust the mantissa for the exponent. A negative exponent moves the binary point to the left. A positive exponent moves the binary point to the right. Because the exponent is 7, the mantissa is adjusted as follows:
  11110000.1000000000000000

• Finally, we have a binary floating-point number. Binary bits that are to the left of the binary point represent the power of two corresponding to their position. For example, 11110000 represents (1 x 27) + (1 x 26) + (1x 25) + (1 x 24) + (0 x 23)+ (0 x 22) + (0 x 21)+ (0 x 20) = 240.

• Binary bits that are to the right of the binary point also represent a power of 2 corresponding to their position. As the digits are to the right of the binary point the powers are negative. For example: .100 represents (1 x 2-1) + (0 x 2-2)+ (0 x 2-3) + … which equals 0.5.

• Adding these two numbers together and making reference to the sign bit produces the number +240.5.

For each floating point value requested two MODBUS Protocol registers (four bytes) must be requested. The received order and
significance of these four bytes for Eastron Digital meters is shown below:

Data Hi Reg,

Hi Byte

| Data Hi Reg,

Lo Byte

| Data Lo Reg,

Hi Byte

| Data Lo Reg,

Lo Byte

---|---|---|---

MODBUS Protocol Commands supported
All Eastron Digital meters support the “Read Input Register” (3X registers), the “Read Holding Register” (4X registers) and the “Pre-set Multiple Registers” (write 4X registers) commands of the MODBUS Protocol RTU protocol. All values stored and returned are in floating point format to IEEE 754 with the most significant register first.

Read Input Registers
MODBUS Protocol code 04 reads the contents of the 3X registers.

Example
The following query will request ‘Volts 1’ from an instrument with node address 1:

• Note: Data must be requested in register pairs i.e. the “Starting Address“ and the “Number of Points” must be even numbers to request a floating point variable. If the “Starting Address” or the “Number of points” is odd then the query will fall in the middle of a floating point variable the product will return an error message.
• The following response returns the contents of Volts 1 as 230.2. But see also “Exception Response” later.

Holding Registers

Read Holding Registers
MODBUS Protocol code 03 reads the contents of the 4X registers.

Example
The following query will request the prevailing ‘Demand Time’:

Note: Data must be requested in register pairs i.e. the “Starting Address“ and the “Number of Points” must be even numbers to request a floating point variable. If the “Starting Address” or the “Number of points” is odd then the query will fall in the middle of a floating point variable the product will return an error message.

The following response returns the contents of Demand Time as 1, But see also “Exception Response” later.

Write Holding Registers
MODBUS Protocol code 10 (16 decimal) writes the contents of the 4X registers.

Example
The following query will set the Demand Period to 60, which effectively resets the Demand Time:

Note: Data must be written in register pairs i.e. the “Starting Address“ and the “Number of Points” must be even numbers to write a floating point variable. If the “Starting Address” or the “Number of points” is odd then the query will fall in the middle of a floating point variable the product will return an error message. In general only one floating point value can be written per query

The following response indicates that the write has been successful. But see also “Exception Response”later.

Exception Response
If the slave in the “Write Holding Register” example above, did not support that function then it would have replied with an Exception Response as shown below. The exception function code is the original function code from the query with the MSB set i.e. it has had 80 hex logically ORed with it. The exception code indicates the reason for the exception. The slave will not respond at all if there is an error with the parity or CRC of the query. However, if the slave can not process the query then it will respond with an exception. In this case a code 01, the requested function is not support by this slave.

Exception Codes

Table of Exception Codes
Eastron Digital meters support the following function codes:

to read or write part of a floating point value
03| Illegal Data Value| Attempt to set a floating point variable to an invalid value
05| Slave Device Failure| An error occurred when the instrument attempted to store an update to it’s configuration

Diagnostics
MODBUS Protocol code 08 provides a number of diagnostic sub-functions. Only the “Return Query Data” sub-function (sub-function 0) is
supported on Eastron Digital meters.

Example
The following query will send a diagnostic “return query data” query with the data elements set to Hex(AA) and Hex(55) and will expect
these to be returned in the response:

Note: Exactly one register of data (two bytes) must be sent with this function.

The following response indicates the correct reply to the query, i.e. the same bytes as the query.

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References

• Amazon.de: Hochwertiger Energiezähler

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