Satec PM171 series User manual

Series PM171
Powermeters
Modbus
Communications
Protocol
Reference
Guide
BG0236Rev. A2

SERIES PM171 POWERMETERS
COMMUNICATIONS
Modbus Communications Protocol
REFERENCE GUIDE

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Every effort has been made to ensure that the material herein is complete and accurate. However, the
manufacturer is not responsible for any mistakes in printing or faulty instructions contained in this book.
Notification of any errors or misprints will be received with appreciation.
For further information regarding a particular installation, operation or maintenance of equipment,
contact the manufacturer or your local representative or distributor.
This book is copyrighted. No part of this book may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise
without the prior written permission of the manufacturer.
Modbus is a trademark of Modicon, Inc.
BG0236 Rev.A2

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Table of Contents
1 GENERAL ......................................................................................................4
2 MODBUS FRAMING ......................................................................................5
2.1 Transmission Mode............................................................................................................5
2.2 The RTU Frame Format ....................................................................................................5
2.3 Address Field.....................................................................................................................5
2.4 Function Field.....................................................................................................................5
2.5 Data Field...........................................................................................................................6
2.6 Error Check Field...............................................................................................................6
3 MODBUS MESSAGE FORMATS...................................................................7
3.1 Function 03 - Read Multiple Registers...............................................................................7
3.2 Function 04 - Read Multiple Registers...............................................................................7
3.3 Function 06 - Write Single Register...................................................................................7
3.4 Function 16 - Write Multiple Registers...............................................................................8
3.5 Function 08 - Loop-back Communications Test................................................................8
3.6 Exception Responses ........................................................................................................9
4 PROTOCOL IMPLEMENTATION.................................................................10
4.1 Modbus Register Addresses............................................................................................10
4.2 Data Formats...................................................................................................................10
4.2.1 16-bit Integer Format................................................................................................10
4.2.2 32-bit Modulo 10000 Format....................................................................................11
4.2.3 32-bit Long Integer Format.......................................................................................11
4.3 User Assignable Registers...............................................................................................11
4.4 Configuring and Accessing Log Files...............................................................................12
5 POWERMETER REGISTERS DESCRIPTION.............................................13
5.1 Basic Data Registers........................................................................................................13
5.2 Basic Setup Registers......................................................................................................14
5.3 User Selectable Options Setup Registers........................................................................15
5.4 Communications Setup Registers....................................................................................16
5.5 Reset/Clear Registers......................................................................................................16
5.6 Instrument Status Registers.............................................................................................17
5.7 Extended Status Registers...............................................................................................17
5.8 Memory Status Registers.................................................................................................20
5.9 Extended Data Registers.................................................................................................20
5.10 Analog Output Setup Registers......................................................................................27
5.11 Analog Expander Setup Registers.................................................................................27
5.12 Digital Inputs Allocation Registers..................................................................................29
5.13 Timers Setup Registers .................................................................................................29
5.14 Alarm/Event Setpoints Registers ...................................................................................29
5.15 Pulsing Setpoints Registers...........................................................................................32
5.16 Relay Operation Control Registers ................................................................................33
5.17 Pulse Counters Setup Registers....................................................................................33
5.18 Log Memory Partitions Setup Registers.........................................................................34
5.19 Data Log Setup Registers..............................................................................................35
5.20 Event Log Registers.......................................................................................................35
5.21 Data Log Registers ........................................................................................................37
5.22 Min/Max Log Registers ..................................................................................................37
5.23 Real Time Clock Registers ............................................................................................38
5.24 TOU System Registers Setup........................................................................................39
5.25 TOU Daily Profiles Registers .........................................................................................40
5.26 TOU Calendar Registers................................................................................................41
5.27 TOU Calendar Years Registers .....................................................................................41

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1 GENERAL
This document specifies a subset of the Modbus serial communications protocol used to transfer data
between a master computer station and the PM171. The document provides the complete information
necessary to develop a third-party communications software capable of communication with the Series
PM171 Powermeters. Additional information concerning communications operation, configuring the
communications parameters, and communications connections is found in "Series PM171
Powermeters, Installation and Operation Manual".
IMPORTANT
1. The voltage parameters throughout the protocol can represent line-to-neutral or line-to-line voltages
depending on the wiring mode selected in the instrument. When the 4LN3 or 3LN3 wiring mode is
selected, the voltages will be line-to-neutral; for any other wiring mode, they will be line-to-line voltages.
In 4LN3, 4LL3, 3LN3 and 3LL3 wiring modes, harmonic voltages will represent line-to-neutral voltages.
In a 3-wire direct connection, harmonic voltages will represent line-to-neutral voltages as they appear on
the instrument's input transformers. In a 3-wire open delta connection, harmonic voltages will comprise
L12 and L23 line-to-line voltages.
2. In 3-wire connection schemes, the unbalanced current and phase readings for power factor, active
power, and reactive power will be zeros, because they have no meaning. Only the total three-phase
power values can be used.
3. Most of the instrument's advanced features are configured using multiple setup parameters that can be
accessed in certain contiguous registers. When writing the setup registers, it is recommended to write
all the registers at once using a single request, or to clear (zero) the setup before writing into separate
registers.

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2 MODBUS FRAMING
2.1 Transmission Mode
The protocol uses the Modbus Remote Terminal Unit (RTU) transmission mode. In RTU mode, data is
sent in 8-bit binary characters. The 8 bit even parity or 8 bit no parity data format must be selected
when configuring the instrument communications. The data format is shown in the following table.
Table 2-1 RTU Data Format
Field No. of bits
Start bit 1
Data bits 8
Parity (optional) 1
Stop bit 1
Least significant bit first
2.2 The RTU Frame Format
Frame synchronization is maintained in RTU transmission mode by simulating a synchronization
message. The receiving device monitors the elapsed time between receptions of characters. If three
and one-half character times elapse without a new character or completion of the frame, then the
device flushes the frame and assumes that the next byte received will be an address. The frame
format is defined below.
The maximum query and response message length is 256 bytes including check characters.
RTU Message Frame Format
T1 T2 T3 Address Function Data CRC Check T1 T2 T3
8 bits 8 bits N * 8 bits 16 bits
2.3 Address Field
The address field contains a user assigned address (1-247) of the instrument that is to receive a
message. Address 0 is used in broadcast mode to transmit to all instruments (broadcast mode is
available only for functions 06 and 16). In this case all instruments receive the message and take
action on the request, but do not issue a response. In the PM171, the broadcast mode is supported
only for register addresses 287-294 and 301-302 (reset energies and maximum demands), 3404-3415
(reset/clear registers), and 4352-4358 (real-time clock registers).
2.4 Function Field
The function field contains a function code that tells the instrument what action to perform. Function
codes used in the protocol are shown below in Table 2-2.
Table 2-2 Modbus Function Codes
Code
(decimal) Meaning in Modbus Action
03 Read holding registers Read multiple registers
04 Read input registers Read multiple registers
06 Preset single register Write single register
16 Preset multiple registers Write multiple registers
08 Loop-back test Communications test
NOTE Broadcast mode available only for functions code 06 and 16.

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2.5 Data Field
The data field contains information needed by the instrument to perform a specific function, or data
collected by the instrument in response to a query.
IMPORTANT Fields composed of two bytes are sent in the order high byte first, low byte second.
2.6 Error Check Field
The error check field contains the Cyclical Redundancy Check (CRC) word. The start of the message
is ignored in calculating the CRC. The CRC-16 error check sequence is implemented as described in
the following paragraphs.
The message (data bits only, disregarding start/stop and optional parity bits) is considered one
continuous binary number whose most significant bit (MSB) is transmitted first. The message is pre-
multiplied by x16 (shifted left 16 bits), and then divided by x16 + x15 + x2 + 1 expressed as a binary
number (11000000000000101). The integer quotient digits are ignored and the 16-bit remainder
(initialized to all ones at the start to avoid the case of all zeros being an accepted message) is
appended to the message (MSB first) as the two CRC check bytes. The resulting message including
CRC, when divided by the same polynomial (x16 + x15 + x2 + 1) at the receiver will give a zero
remainder if no errors have occurred. (The receiving unit recalculates the CRC and compares it to the
transmitted CRC). All arithmetic is performed modulo two (no carries).
The device used to serialize the data for transmission will send the conventional LSB or right-most bit
of each character first. In generating the CRC, the first bit transmitted is defined as the MSB of the
dividend. For convenience, and since there are no carries used in the arithmetic, let's assume while
computing the CRC that the MSB is on the right. To be consistent, the bit order of the generating
polynomial must be reversed. The MSB of the polynomial is dropped since it affects only the quotient
and not the remainder. This yields 1010 0000 0000 0001 (Hex A001). Note that this reversal of the bit
order will have no effect whatever on the interpretation or bit order of characters external to the CRC
calculations.
The step by step procedure to form the CRC-16 check bytes is as follows:
1. Load a 16-bit register with all 1's.
2. Exclusive OR the first 8-bit byte with the low order byte of the 16-bit register, putting the result in the 16-bit
register.
3. Shift the 16-bit register one bit to the right.
4a. If the bit shifted out to the right (flag) is one, exclusive OR the generating polynomial 1010 000 000 0001
with the 16-bit register.
4b. If the bit shifted out to the right is zero, return to step 3.
5. Repeat steps 3 and 4 until 8 shifts have been performed.
6. Exclusive OR the next 8-bit byte with the 16-bit register.
7. Repeat step 3 through 6 until all bytes of the message have been exclusive ORed with the 16-bit register
and shifted 8 times.
8. When the 16-bit CRC is transmitted in the message, the low order byte will be transmitted first, followed by
the high order byte.
For detailed information about CRC calculation, refer to the Modbus Protocol Reference Guide.

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3 MODBUS MESSAGE FORMATS
3.1 Function 03 - Read Multiple Registers
This command allows the user to obtain contents of up to 125 contiguous registers from a single data
table.
Request
Instrument
Address Function (03) Starting Address Word Count Error Check
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Starting Address Address of the first register to be read
Word Count The number of contiguous words to be read
Response
Instrument
Address Function (03) Byte Count Data Word 1 ... Data Word N Error Check
1 byte 1 byte 1 byte 2 bytes ... 2 bytes 2 bytes
The byte count field contains quantity of bytes to be returned.
3.2 Function 04 - Read Multiple Registers
This command allows the user to obtain contents of up to 125 contiguous registers from a single data
table. It can be used instead of function 03.
Request
Instrument
Address Function (04) Starting Address Word Count Error Check
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Starting Address Address of the first register to be read
Word Count The number of contiguous words to be read
Response
Instrument
Address Function (04) Byte Count Data Word 1 ... Data Word N Error Check
1 byte 1 byte 1 byte 2 bytes ... 2 bytes 2 bytes
The byte count field contains quantity of bytes to be returned.
3.3 Function 06 - Write Single Register
This command allows the user to write the contents of a data register in any data table where a register
can be written.
Request
Instrument
Address Function (06) Starting Address Data Word Error check
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Starting Address Address of the register to be written
Data Value Data to be written to the register
Response
The normal response is the retransmission of the write request.

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3.4 Function 16 - Write Multiple Registers
This request allows the user to write the contents of multiple contiguous registers to a single data table
where registers can be written.
Request
Instrument
Address Function (16) Starting Address Word Count Byte Count
1 byte 1 byte 2 bytes 2 bytes 1 byte
Data Word 1 ... ... ... Data Word N Error Check
2 bytes ... ... ... 2 bytes 2 bytes
Starting Address Address of the first register to be written
Word Count The number of contiguous words to be written
Byte Count The number of bytes to be written
Response
Instrument
Address Function (16) Starting Address Word Count Error Check
1 byte 1 byte 2 bytes 1 word 2 bytes
3.5 Function 08 - Loop-back Communications Test
The purpose of this request is to check the communications link between the specified instrument and
PC.
Request
Instrument
Address Function (08) Diagnostic Code (0) Data Error Check
1 byte 1 byte 2 bytes 2 bytes 2 bytes
Diagnostic Code Designates action to be taken in Loop-back test. The protocol supports only Diagnostic
Code 0 - return query data.
Data Query data. The data passed in this field will be returned to the master through the
instrument. The entire message returned will be identical to the message transmitted by the
master, field-per-field.
Response
Instrument
Address Function (08) Diagnostic Code (0) Data Error Check
1 byte 1 byte 2 bytes 2 bytes 2 bytes
The normal response is the re-transmission of a test message.

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3.6 Exception Responses
The instrument sends an exception response when errors are detected in the received message. To
indicate that the response is notification of an error, the high order bit of the function code is set to 1.
Exception Response
Instrument
Address Function (high order bit is set to 1) Exception Code Error Check
1 byte 1 byte 1 byte 2 byte
Exception response codes:
01 - Illegal function
02 - Illegal data address
03 - Illegal data value
06 - Busy, rejected message. The message was received without error, but the instrument is being
programmed from the keypad (only for requests accessing setup registers).
NOTE When the character framing, parity, or redundancy check detects a communication error, processing of
the master's request stops. The instrument will not act on or respond to the message.

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4 PROTOCOL IMPLEMENTATION
4.1 Modbus Register Addresses
The PM171 Modbus registers are referred to by using addresses in the range of 0 to 65535. From
within the Modbus applications, the PM171 Modbus registers can be accessed by simulating holding
registers of the Modicon 584, 884 or 984 Programmable Controller, using a 5-digit “4XXXX” or 6-digit
“4XXXXX” addressing scheme. To map the PM171 register address to the range of the Modbus
holding registers, add a value of 40001 to the PM171 register address. When a register address
exceeds 9999, use a 6-digit addressing scheme by adding 400001 to the PM171 register address.
4.2 Data Formats
The PM171 uses three data formats to pass data between a master application and the instrument: a
16-bit integer format, a 32-bit modulo 10000 format, and a 32-bit long integer format.
4.2.1 16-bit Integer Format
A 16-bit data is transmitted in a single 16-bit Modbus register as unsigned or signed integer (whole)
numbers without conversion or using pre-scaling to accommodate large-scale and fractional numbers
to a 16-bit register format. Scaling can be made using either the LIN3 linear conversion, or decimal
pre-scaling to pass fractional numbers in integer format.
Non-scaled data
The data will be presented exactly as retrieved by the communications program from the instrument.
The value range for unsigned data is 0 to 65535; for signed data the range is -32768 to 32767.
LIN3 (Linear) Scaling
This conversion maps the raw data received by the communications program in the range of 0 - 9999
onto the user-defined LO scale/HI scale range. The conversion is carried out according to the formula:
Y = (X / 9999) ×(HI - LO) + LO
where:
Y - the true value in engineering units
X - the raw input data in the range of 0 - 9999
LO, HI - the data low and high scales in engineering units
When data conversion is necessary, the HI and LO scales, and data conversion method are indicated
for the corresponding registers.
EXAMPLE
Suppose you have read a value of 5000 from register 256 that contains a voltage reading (see Table 5-1). If your
instrument has the 144V input option, and you use potential transformers with the ratings of
22,000V : 110V = 200, then the voltage high scale is HI = 144×200 = 28,800, and in accordance with the above
formula, the voltage reading in engineering units will be as follows:
5000
×(28800 - 0)/9999 + 0 = 14401V
When a value is written to the instrument, the conversion is carried out in reverse to produce the
written value in the range of 0 - 9999:
X = 9999
×(Y - LO) / (HI - LO)
Decimal Scaling
Decimal pre-scaling can be used to accommodate fractional numbers to an integer register format.
Fractional numbers pre-multiplied by 10 in power N, where N is the number of digits in the fractional
part. For example, the frequency reading of 50.01 Hz is transmitted as 5001, having been pre-
multiplied by 100. Whenever a data register contains a fractional number, the register measurement
unit is given with a multiplier ×0.1, ×0.01 or ×0.001, showing an actual register resolution (the weight of

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the least significant decimal digit). To get an actual fractional number with specified precision, scale the
register value with the given multiplier. To write a fractional number into the register, divide the number
by the given multiplier.
4.2.2 32-bit Modulo 10000 Format
The short energy registers 287-294, and 301-302 are transmitted in two contiguous 16-bit registers in
modulo 10000 format. The first (low order) register contains the value mod 10000, and the second
(high order) register contains the value/10000. To get the true energy reading, the high order register
value should be multiplied by 10,000 and added to the low order register.
4.2.3 32-bit Long Integer Format
In a 32-bit long integer format, data is transmitted in two adjacent 16-bit Modbus registers as unsigned
or signed long integer (whole) numbers. The first register contains the low-order word (lower 16 bits)
and the second register contains the high order word (higher 16 bits) of the 32-bit long number. The
low-order word always starts at an even Modbus address. The value range for unsigned data is 0 to
4,294,967,295; for signed data the range is -2,147,483,648 to 2,147,483,647.
A 32-bit data can be transmitted without conversion as is, or by using decimal pre-scaling to transform
fractional numbers to an integer format as described above (see Decimal Scaling in Section 4.2.1).
4.3 User Assignable Registers
The PM171 contains the 120 user assignable registers in the address range of 0 to 119 (see Table
4-1), any of which you can map to either register address accessible in the instrument. Registers that
reside in different locations may be accessed by a single request by re-mapping them to adjacent
addresses in the user assignable registers area.
The actual addresses of the assignable registers which are accessed via addresses 0 to 119 are
specified in the user assignable register map (see Table 4-2). This map occupies addresses from 120
to 239, where map register 120 should contain the actual address of the register accessed via
assignable register 0, register 121 should contain the actual address of the register accessed via
assignable register 1, and so on. Note that the assignable register addresses and the map register
addresses may not be re-mapped.
To build your own register map, write to map registers (120 to 239) the actual addresses you want to read from
or write to via the assignable area (0 to 119). Note that long word registers should always be aligned at even
addresses.For example, if you want to read registers 7136 (real-time voltage of phase A, word) and 7576/7577
(kWh import, long word) via registers 0-2, then do the following:
- write 7576 to register 120
- write 7577 to register 121
- write 7136 to register 122
Reading from registers 0-2 will return the kWh reading in registers 0 (low word) and 1 (high word), and the
voltage reading in register 2.
Table 4-1 User Assignable Registers
Register contents Register Size, byte Direction Range
User definable data 0 0 
User definable data 1 1 
User definable data 2
... 2 ... 
... 
... 
...
User definable data 119 119 
- depends on the mapped register

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Table 4-2 User Assignable Register Map
Register contents Register Size, byte Direction Range
Register address for user data 0 120 2 R/W 240 to 65535
Register address for user data 1 121 2 R/W 240 to 65535
Register address for user data 2
... 122 ... 2 ... R/W ... 240 to 65535 ...
Register address for user data 119 239 2 R/W 240 to 65535
4.4 Configuring and Accessing Log Files
Configuring Memory for Logging
To use the onboard data logging, allocate a separate log partition for each specific data you want to be
recorded in your instrument. The PM171E provides concurrent recording data in 9 different memory
partitions, one of which is intended to record event log data and the others to store 8 different data logs
using different sets of data parameters. Refer to Section 5.18 for information on how to allocate a
memory partition for your specific data. Refer to Section 5.19 on how to configure a set of parameters
to be recorded to each data log.
Each memory partition you allocated for logging is organized as a sequential file of records where all
data is recorded in chronological order with a time and date stamp. When a partition is filled up,
recording can be stopped or can continue over the oldest records if you specified a partition with a
wrap-around (circular) attribute.
Accessing Log Files
Each log file has a separate file read pointer which always points to the current file record that will be
read next, and a separate register window which gives access to the record pointed to by this pointer.
Initially, the read pointer is associated with the oldest record in the file. Reading a record via the file
window returns the current record data, and then the pointer automatically advances to the following
record in the file. Consequent requests addressed to the file window will return a new record each time
in the direction from the oldest record to the more recent records. Because the file window advances
automatically after the instrument responds to the master request (regardless of the number of
registers in the window being accessed), the entire window must be read at once using a single
request.
The instrument provides sequential reading of a file records until the end of a file is reached. When a
record is requested after the end of a file, the response message will contain a zero record with an
exception code indicating the end of a log file. Refer to Sections 5.20 and 5.21 for information on read
requests you can use to access your log files.
You can also use the instrument reset registers (see Section 5.5) to restore the file read pointer to the
oldest record in your log file if you want to re-read the file from the beginning. Take into consideration
the fact that in a wrap-around (circular) log partition, the oldest records may be overwritten by the most
recent records since you have read them.

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5 POWERMETER REGISTERS DESCRIPTION
5.1 Basic Data Registers
Table 5-1 Basic Data Registers
Parameter Register Size, Direc- Unit Scale Con-
byte tion Low High version
Voltage L1/L12 256 2 R 1V 0 Vmax LIN3
Voltage L2/L23 257 2 R 1V 0 Vmax LIN3
Voltage L3/L31 258 2 R 1V 0 Vmax LIN3
Current L1 259 2 R 1A 0 Imax LIN3
Current L2 260 2 R 1A 0 Imax LIN3
Current L3 261 2 R 1A 0 Imax LIN3
kW L1 262 2 R 1kW -Pmax Pmax LIN3
kW L2 263 2 R 1kW -Pmax Pmax LIN3
kW L3 264 2 R 1kW -Pmax Pmax LIN3
kvar L1 265 2 R 1kvar -Pmax Pmax LIN3
kvar L2 266 2 R 1kvar -Pmax Pmax LIN3
kvar L3 267 2 R 1kvar -Pmax Pmax LIN3
kVA L1 268 2 R 1kVA -Pmax Pmax LIN3
kVA L2 269 2 R 1kVA -Pmax Pmax LIN3
kVA L3 270 2 R 1kVA -Pmax Pmax LIN3
Power factor L1 271 2 R 0.001 -1.000 1.000 LIN3
Power factor L2 272 2 R 0.001 -1.000 1.000 LIN3
Power factor L3 273 2 R 0.001 -1.000 1.000 LIN3
Total power factor 274 2 R 0.001 -1.000 1.000 LIN3
Total kW 275 2 R 1kW -Pmax Pmax LIN3
Total kvar 276 2 R 1kvar -Pmax Pmax LIN3
Total kVA 277 2 R 1kVA -Pmax Pmax LIN3
Neutral current 278 2 R 1A 0 Imax LIN3
Frequency 279 2 R 0.01Hz 45.00 65.00 LIN3
Max. sliding window kW
demand (E) 280 2 R/W 1kW -Pmax Pmax LIN3
Accumulated kW
demand (E) 281 2 R/W 1kW -Pmax Pmax LIN3
Max. sliding window kVA
demand (E) 282 2 R/W 1kVA -Pmax Pmax LIN3
Accumulated kVA
demand (E) 283 2 R/W 1kVA -Pmax Pmax LIN3
Max. ampere demand L1 284 2 R/W 1A 0 Imax LIN3
Max. ampere demand L2 285 2 R/W 1A 0 Imax LIN3
Max. ampere demand L3 286 2 R/W 1A 0 Imax LIN3
kWh import (low) (E) 287 2 R/W 1kWh 0 9999 NONE
kWh import (high) (E) 288 2 R/W 10,000 kWh 0 9999 NONE
kWh export (low) (E) 289 2 R/W 1kWh 0 9999 NONE
kWh export (high) (E) 290 2 R/W 10,000 kWh 0 9999 NONE
+kvarh net (low) (E) 291 2 R/W 1kvarh 0 9999 NONE
+kvarh net (high) (E) 292 2 R/W 10,000 kvarh 0 9999 NONE
-kvarh net (low) (E) 293 2 R/W 1kvarh 0 9999 NONE
-kvarh net (high) (E) 294 2 R/W 10,000 kvarh 0 999 NONE
Voltage THD L1/L12 295 2 R 0.1% 0 999.9 LIN3
Voltage THD L2/L23 296 2 R 0.1% 0 999.9 LIN3
Voltage THD L3 297 2 R 0.1% 0 999.9 LIN3
Current THD L1 298 2 R 0.1% 0 999.9 LIN3
Current THD L2 299 2 R 0.1% 0 999.9 LIN3
Current THD L3 300 2 R 0.1% 0 999.9 LIN3
kVAh (low) (E) 301 2 R/W 1kVAh 0 9999 NONE
kVAh (high) (E) 302 2 R/W 10,000 kVAh 0 9999 NONE
Present sliding window
kW demand (E) 303 2 R 1kW -Pmax Pmax LIN3
Present sliding window
kVA demand (E) 304 2 R 1kVA -Pmax Pmax LIN3
PF at maximum kVA
siding window demand 305 2 R 0.001 -1.000 1.000 LIN3

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Parameter Register Size, Direc- Unit Scale Con-
byte tion Low High version
Current TDD L1 306 2 R 0.1% 0 100.0 LIN3
Current TDD L2 307 2 R 0.1% 0 100.0 LIN3
Current TDD L3 308 2 R 0.1% 0 100.0 LIN3
The parameter limits are as follows:
Imax (20% over-range) = 1.2 ×CT primary current [A]
Direct wiring (PT Ratio = 1):
Vmax (690 V input option) = 828.0 V
Vmax (120 V input option) = 144.0 V
Wiring via PTs (PT Ratio > 1):
Vmax (690 V input option) = 144 ×PT Ratio [V]
Vmax (120 V input option) = 144 ×PT Ratio [V]
Pmax = (Imax ×Vmax ×3)/1000 [kW ] if wiring mode is 4LN3 or 3LN3
Pmax = (Imax ×Vmax ×2)/1000 [kW ] if wiring mode is 4LL3, 3OP2, 3DIR2, 3OP3 or 3LL3
Positive readings of kvarh net
Negative readings of kvarh net
To get block interval demand readings, specify the number of demand periods equal to 1 (see Table 5-2).
When the 4LN3 or 3LN3 wiring mode is selected, the voltages will be line-to-neutral; for any other wiring
mode, they will be line-to-line voltages.
(E) available in the PM171E
NOTE Writing a zero to one of registers 280-286 causes reset of all maximum demands. Writing a zero to one
of registers 287-294 and 301-302 causes reset of all accumulated energies. This does not apply to the
TOU system registers.
5.2 Basic Setup Registers
Table 5-2 Basic Setup Registers
Parameter Register Size,
byte Direc- tion Range
Wiring mode 2304 2 R/W 0 = 3OP2, 1 = 4LN3,
2 = 3DIR2, 3 = 4LL3, 4 = 3OP3,
5 = 3LN3, 6 = 3LL3
PT ratio 2305 2 R/W 10 to 65000 ×0.1
CT primary current 2306 2 R/W 1 to 50000 A
Power demand period (E) 2307 2 R/W 1,2,5,10,15,20,30,60 min,
255 = external synchronization
Volt/ampere demand period 2308 2 R/W 0 to 1800 sec
Averaging buffer size 2309 2 R/W 8, 16, 32
Reset enable/disable 2310 2 R/W 0 = disable, 1 = enable
Reserved 2311 2 R Read as 65535
The number of demand periods (E) 2312 2 R/W 1 to 15
Reserved 2313 2 R Read as 65535
Reserved 2314 2 R Read as 65535
Nominal frequency 2315 2 R/W 50, 60, 25 (Hz)
Maximum demand load current 2316 2 R/W 0 to 50,000 A
(0 = CT primary current)
The wiring mode options are as follows:
3OP2 - 3-wire open delta using 2 CTs (2 element)
4LN3 - 4-wire WYE using 3 PTs (3 element), line to neutral voltage readings
3DIR2 - 3-wire direct connection using 2 CTs (2 element)
4LL3 - 4-wire WYE using 3 PTs (3 element), line to line voltage readings
3OP3 - 3-wire open delta using 3 CTs (2 1/2 element)
3LN3 - 4-wire WYE using 2 PTs (2 1/2 element), line to neutral voltage readings
3LL3 - 4-wire WYE using 2 PTs (2 1/2 element), line to line voltage readings
25 Hz - special order
(E) available in the PM171E

15
5.3 User Selectable Options Setup Registers
Table 5-3 User Selectable Options Registers
Parameter Register Size,
byte Direc- tion Range
Power calculation mode 2376 2 R/W 0 = using reactive power,
1 = using non-active power
Energy roll value (E) 2377 2 R/W
0 = 1×104
1 = 1×105
2 = 1×106
3 = 1×107
4 = 1×108
5 = 1×109
Phase energy calculation mode (E) 2378 2 R/W 0 = disable, 1 = enable
Analog output option 2379 2 R/W 0 = none
1 = 0-20 mA
2 = 4-20 mA
3 = 0-1 mA
4 = ±1 mA
Analog expander output 2380 2 R/W 0 = none
1 = 0-20 mA
2 = 4-20 mA
3 = 0-1 mA
4 = ±1 mA
(E) available in the PM171E (read as 65535 in the PM171P)
For short energy registers (see Table 5-1), the maximum roll value will be 1×108 for positive readings and
1×107for negative readings.
Do not enable the analog expander output if the analog expander is not connected to the instrument,
otherwise the computer communications will become garbled.

16
5.4 Communications Setup Registers
Table 5-4 Communications Setup Registers
Parameter Register Size,
byte Direc- tion Range
Reserved 2344 2 R
Read as 65535
Interface 2345 2 R/W 0 = RS-232
1 = RS-422
2 = RS-485
Address 2346 2 R/W 1 to 247
Baud rate 2347 2 R/W 0 = 110 bps
1 = 300 bps
2 = 600 bps
3 = 1200 bps
4 = 2400 bps
5 = 4800 bps
6 = 9600 bps
7 = 19200 bps
Data format 2348 2 R/W 1 = 8 bits/no parity
2 = 8 bits/even parity
Incoming flow control
(handshaking) 2349 2 R/W 0 = no handshaking 1 = software handshaking
(XON/XOFF protocol)
2 = hardware handshaking
(CTS protocol)
Outgoing flow control
(RTS/DTR) 2350 2 R/W 0 = RTS signal not used 1 = RTS permanently
asserted (DTR mode)
2 = RTS asserted during the
transmission
When changing the instrument address, baud rate or data format, the new communications parameters will take
effect 100 ms after the instrument responds to the master's request.
5.5 Reset/Clear Registers
Table 5-5 Reset/Clear Registers
Function Register Size,
byte Direc- tion Reset value
Clear total energy registers (E) 3404 2 W 0
Clear total maximum demand
registers 3405 2 W 0 = all maximum demands 1 = power demands (E)
2 = volt/ampere demands
Clear TOU energy registers (E) 3406 2 W 0
Clear TOU maximum demand
registers (E) 3407 2 W 0
Clear pulse counters 3408 2 W 0 = all counters
1-4 = counter #1 - #4
Clear Min/Max log 3409 2 W 0
Clear event log (E) 3410 2 W 0
Clear data log 3411 2 W 0-7 = log #1 - #8
16 = all data logs
Reserved 3412 2
Reserved 3413 2
Reserved 3414 2
Restore event log queue pointer
(E) 3415 2 W 0
Restore data log queue pointer (E) 3416 2 W 0-7 = log #1 - #8
(E) available in the PM171E

17
5.6 Instrument Status Registers
Table 5-6 Instrument Status Registers
Parameter Register Size, Direc- Unit Range
byte tion
Instrument reset
register 2560 2 R/W 0 (when read) 65535 (when written) =
reset the instrument
Reserved 2561 2 R Read as 0
Relay status 2562 2 R see Table 5-7
Reserved 2563 2 R Read as 0
Status inputs 2564 2 R see Table 5-11
Firmware version
number 2565 2 R 0-65535
Instrument options 1 2566 2 R see Table 5-8
Instrument options 2 2567 2 R see Table 5-8
Writing a value of 65535 into register 2560 will cause the instrument to perform a warm restart.
Table 5-7 Relay Status
Bit number Description
0-5 Not used (permanently set to 1)
6 Relay #2 status
7 Relay #1 status
8-15 Not used (permanently set to 0)
Bit meaning: 0 = relay is energized, 1 = relay is not energized
Table 5-8 Instrument Options
Options register Bit Description
Options1 0 120V option
1 690V option
2-3 Reserved
4 100% current over-range
5 Reserved
6 Analog output 0/4-20 mA
7 Analog output 0-1 mA
8
Analog output ±1 mA
9 Relays option
10 Digital inputs option
11-13 Reserved
14
Analog expander output ±1 mA
15 Reserved
Options 2 0-2 Number of relays - 1
3-6 Number of digital inputs - 1
7-8 Number of analog outputs - 1
9-13 Reserved
14-15 Memory module size (PM171E): 10 = 512 Kbytes
5.7 Extended Status Registers
Table 5-9 Extended Status Registers
Parameter Register Size,
byte Direction Value range
Relay status 3452 2 R see Table 5-10
Reserved 3453 2 R Read as 0
Status inputs 3454 2 R see Table 5-11
Setpoints status 3455 2 R see Table 5-12
Log status 3456 2 R see Table 5-13
Data log status 3457 2 R see Table 5-14
Reserved 3458-
3473 2 R Read as 0

18
Parameter Register Size,
byte Direction Value range
Setpoint alarm status 3474 2 R/W see Table 5-15
Self-check alarm status 3475 2 R/W see Table 5-16
Reserved 3476-
3484 2 R Read as 0
Battery status 3485 2 R 0 = low, 1 = normal
Table 5-10 Relay Status
Bit Description
0 Relay #1 status
1 Relay #2 status
2-15 Not used (permanently set to 0)
Bit meaning: 0 = relay is not energized, 1 = relay is energized
Table 5-11 Status Inputs
Bit Description
0 Status input #1
1 Status input #2
2-15 Not used (permanently set to 0)
Bit meaning: 0 = contact open, 1 = contact closed
Table 5-12 Setpoints Status
Bit Description
0 Setpoint # 1 status
1 Setpoint # 2 status
2 Setpoint # 3 status
3 Setpoint # 4 status
4 Setpoint # 5 status
5 Setpoint # 6 status
6 Setpoint # 7 status
7 Setpoint # 8 status
8 Setpoint # 9 status
9 Setpoint # 10 status
10 Setpoint # 11 status
11 Setpoint # 12 status
12 Setpoint # 13 status
13 Setpoint # 14 status
14 Setpoint # 15 status
15 Setpoint # 16 status
Bit meaning: 0 = setpoint is released, 1 = setpoint is operated
Table 5-13 Log Status
Bit Description
0 Reserved
1 New Min/Max Log
2 New event log
3 New data log (any)
4-15 Not used (permanently set to 0)
Bit meaning: 0 = no new logs, 1 = new log recorded (the new log flag is reset when the user reads the first log
record after the flag has been set)

19
Table 5-14 Data Log Status
Bit Description
0 New data log #1
1 New data log #2
2 New data log #3
3 New data log #4
4 New data log #5
5 New data log #6
6 New data log #7
7 New data log #8
4-15 Not used (permanently set to 0)
Bit meaning: 0 = no new logs, 1 = new log recorded (the new log flag is reset when the user reads the first log
record after the flag has been set)
Table 5-15 Setpoint Alarm Status
Bit Description
0 Alarm #1
1 Alarm #2
2 Alarm #3
3 Alarm #4
4 Alarm #5
5 Alarm #6
6 Alarm #7
7 Alarm #8
8 Alarm #9
9 Alarm #10
10 Alarm #11
11 Alarm #12
12 Alarm #13
13 Alarm #14
14 Alarm #15
15 Alarm #16
Bit meaning: 1 = setpoint has been operated
The setpoint alarm register stores the status of the operated setpoints by setting the appropriate bits to 1. The
alarm status bits can be reset all together by writing zero to the setpoint alarm register. It is possible to reset
each alarm status bit separately by writing back the contents of the alarm register with a corresponding alarm bit
set to 0.
Table 5-16 Self-check Alarm Status
Bit Description
0 Reserved
1 ROM error
2 RAM error
3 Watchdog timer reset
4 Sampling failure
5 Out of control trap
6 Reserved
7 Timing failure
8 Loss of power (power up)
9 External reset (warm restart)
10 Configuration corrupted
11 RTC time-synchronization required
12-15 Reserved
The self-check alarm register indicates possible problems with the instrument hardware or setup configuration.
The hardware problems are indicated by the appropriate bits which are set whenever the instrument fails self-test
diagnostics or in the event of loss of power. The setup configuration problems are indicated by the dedicated bit
which is set when either configuration register is corrupted. In this event, the instrument will use the default
configuration. The configuration corrupt bit may also be set as a result of the legal changes in the setup
configuration since the instrument might implicitly change or clear other setups if they are affected by the
changes made.
Hardware fault bits can be reset by writing zero to the self-check alarm register. The configuration corrupt status
bit and RTC synchronization bit are also reset automatically when you change setup or update RTC either via the
front panel or through communications.