Basler Electric BE1-851 User Manual

INSTRUCTION MANUAL

FOR

OVERCURRENT PROTECTION SYSTEM

BE1-851

MODBUS™ PROTOCOL

P0037-40

05-19-06

Publication: 9289900992

Revision: F 02/08

INTRODUCTION

This instruction manual provides detailed information about the BE1-851 Overcurrent Protection System
with the Modbus™ Protocol.

9289900992 Rev F BE1-851 Modbus™ Protocol i

First Printing: May 1997

Printed in USA

© 2008 Basler Electric, Highland Illinois 62249 USA

All Rights Reserved

February 2008

CONFIDENTIAL INFORMATION

of Basler Electric, Highland Illinois, USA. It is loaned for confidential use, subject
to return on request, and with the mutual understanding that it will not be used in
any manner detrimental to the interest of Basler Electric.

It is not the intention of this manual to cover all details and variations in equipment, nor does this manual
provide data for every possible contingency regarding installation or operation. The availability and design
of all features and options are subject to modification without notice. Should further information be
required, contact Basler Electric.

BASLER ELECTRIC

ROUTE 143, BOX 269

HIGHLAND IL 62249 USA

http://www.basler.com, [e-mail]

PHONE [phone] FAX [phone]

ii BE1-851 Modbus™ Protocol 9289900992 Rev F

REVISION HISTORY

The following information provides a historical summary of the changes made to this instruction manual
(9289900992). Revisions are listed in reverse chronological order.

Manual

Revision and Date

F, 02/08
E, 12/06

D, 09/02

C, 03/01

B, 10/99

A, 06/99

—, 05/97

• Added information for style option 1, V and W.

• Updated ASCII Command Versus Modbus™ Register Cross

Reference.

• Added sensing input type “G” options.

• Added manual part number and revision to footers.

• Corrected pagination error occurring at page 30.

• Corrected table of contents margins.

• Corrected heading level 2 alignments.

• Changed the format of the manual to current standards and other
Modbus™ manuals.

• Corrected Floating Point Data Format on page 7.

• Added conventions on Password Security on pages 13 and 14.

• Added register 40989 on page 17.

• Expanded Notes on registers 40001 to 40006.

• Corrected the value of # for Report Focus in the table on page 35.

• Inserted paragraph under Global Parameters on page 36.

• Added register 40989 to Serial Port Setting Parameters on page 42.

• Corrected minor errors in the manual and SN registers 43498 to

43900 ordering.

• Added new registers 41110 to 41133 (Breaker Block Logic Mask),
41118 to 41121 (Breaker Block Logic Term), 41269 to 41270 (Logic
Alarm Mask), 41403 to 41406 (Reset Target Logic Mask), 41411 to
41414 (Reset Target Logic Term), 41419 to 41422 (Reset Alarm
Logic Mask), 41427 to 41430 (Reset Alarm Logic Term), and 47486
(Reset Logic Alarm Information).

• Updated register 40039 to support report #2 RA-LGC report.

• Added the Modbus™ Write support registers.

• Initial release.

Change

9289900992 Rev F BE1-851 Modbus™ Protocol iii

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iv BE1-851 Modbus™ Protocol 9289900992 Rev F

CONTENTS

SECTION 1 • GENERAL INFORMATION ................................................................................................ 1-1

SECTION 2 • REGISTER TABLE............................................................................................................. 2-1

SECTION 3 • REGISTER DETAILS ......................................................................................................... 3-1

SECTION 4 • ASCII CROSS REFERENCE ............................................................................................. 4-1

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vi BE1-851 Modbus™ Protocol 9289900992 Rev F

SECTION 1 • GENERAL INFORMATION

INTRODUCTION

This document describes the Modbus™ communications protocol employed by BE1-851 relays and how
to exchange information with BE1-851 relays over a Modbus™ network. The BE1-851 communicates by
emulating a subset of the Modicon 984 Programmable Controller.

FUNCTIONAL DESCRIPTION

Modbus™ communications use a master-slave technique in which only the master can initiate a
transaction. This transaction is called a query. When appropriate, a slave (BE1-851) responds to the
query. When a Modbus™ master communicates with a slave, information is provided or requested by the
master. Information residing in the BE1-851 is grouped categorically as follows:

• Session Parameters

• Global Parameters

• Control Parameters (Select Before Operate)

• Setting Parameters

• Report Parameters

• Metering Parameters

All supported data can be read as specified in the register table. Abbreviations are used in the Register
Table to indicate the register type. Register types are:

• Read/Write = RW

• Read Only = R -

Select Before Operate (SBO) functions are used to change active settings groups and control outputs.
There are two settings groups in the BE1-851, one of which may be selected as active using SBO
commands.

When a slave receives a query, the slave responds by either supplying the requested data to the master
or performing the requested action. A slave device never initiates communications on the Modbus™ and
will always generate a response to the query unless certain error conditions occur. The BE1-851 is
designed to communicate on the Modbus™ only as a slave device.

A master can query slaves individually or universally. A universal (“broadcast”) query, when allowed,
evokes no response from any slave device. If a query to an individual slave device requests actions
unable to be performed by the slave, the slave response message contains an exception response code
defining the error detected. Exception response codes are quite often enhanced by the information found
in the “Error Details” block of holding registers.

Message Structure

Master initiated queries and BE1-851 responses share the same message structure. Each message is
comprised of four message fields. They are:

• Device Address (1 byte)

• Function Code (1 byte)

• Data Block (n bytes)

• Error Check field (2 bytes)

Device Address Field

The device address field contains the unique Modbus™ address of the slave being queried. The
addressed slave repeats the address in the device address field of the response message. This field is 1
byte.

Although Modbus™ protocol limits a device address from 1 - 247, a BE1-851 can be assigned a device
address in the range of 1 - 65534. The address is user-selectable at installation and can be altered during
real-time operation.

9289900992 Rev F BE1-851 Modbus™ Protocol 1-1

Function Code Field

The function code field in the query message defines the action to be taken by the addressed slave. This
field is echoed in the response message and is altered by setting the most significant bit (MSB) of the
field to 1 if the response is an error response. This field is 1 byte.

The BE1-851 maps all available data into the Modicon 984 holding register address space (4XXXX) and
supports the following function codes:

• Function 03 (03 hex) - read holding registers

• Function 06 (06 hex) - preset single register (write single holding register)

• Function 08 (08 hex), subfunction 00 - diagnostics: return query data

• Function 08 (08 hex), subfunction 01 - diagnostics: restart communications option

• Function 08 (08 hex), subfunction 04 - diagnostics: force listen only mode

• Function 16 (10 hex) - preset multiple registers, non-broadcast and broadcast

Data Block Field

The query data block contains additional information needed by the slave to perform the requested
function. The response data block contains data collected by the slave for the queried function. An error
response will substitute an exception response code for the data block. The length of this field varies with
each query. See the paragraphs on Register Definitions in this manual for interpretation of data.

Error Check Field

The error check field provides a method for the slave to validate the integrity of the query message
contents and allows the master to confirm the validity of response message contents. This field is 2 bytes.

Serial Transmission Details

A standard Modbus™ network offers two transmission modes for communication: ASCII or remote
terminal unit (RTU). The BE1-851 supports only the RTU mode.

Each 8-bit byte in a message contains two 4-bit hexadecimal characters. The message is transmitted in a
continuous stream with the LSB of each byte of data transmitted first. Transmission of each 8-bit data
byte occurs with one start bit and either one or two stop bits. Parity checking is performed, when enabled,
and can be either odd or even. The transmission baud rate is user-selectable and can be set at
installation and altered during real-time operation. The BE1-851 Modbus™ supported baud rates are
2400, 4800, 9600, and 19200. The factory default baud rate is 9600.

BE1-851 supports both RS-232-C and RS-485 compatible serial interfaces. Both interfaces are
accessible from the rear panel of the BE1-851. The RS-232-C interfaces (front and rear) are configured
for ASCII command mode while the RS-485 interface is configured for Modbus™ communication when
this option is installed. The eighth character of the relay style number must be “1” for the relay to be
configured for Modbus™.

Message Framing and Timing Considerations

When receiving a message, the BE1-851 requires an inter-byte latency of 3.5 character times before
considering the message complete.

Once a valid query is received, the BE1-851 waits a specified amount of time before responding. This
time delay is set in the remote delay time parameter with the SG-COM ASCII command. This parameter
contains a value from 10 - 200 milliseconds. The default value is 10 milliseconds.

Table 1-1 provides the response message transmission time (in seconds) and 3.5 character times (in
milliseconds) for various message lengths and baud rates.

Table 1-1. Timing Considerations

Baud Rate 3.5 Character Time (mSec)

Message Tx Time (seconds)

128 Bytes 256 Bytes

2400 16.04 0.59 1.17
4800 8.021 0.29 0.59
9600 4.0104 0.15 0.29

19200 2.0052 0.07 0.15

1-2 BE1-851 Modbus™ Protocol 9289900992 Rev F

Error Handling and Exception Responses

Any query received that contains a non-existent device address, a framing error, or CRC error is ignored.
No response is transmitted. Queries addressed to a BE1-851 with an unsupported function or illegal
values in the data block result in an error response message with an exception response code. The
exception response codes supported by the BE1-851 are provided in Table 1-2.

Table 1-2. Supported Exception Response Codes

Code Name Meaning

01 Illegal Function

02 Illegal Data Address

03 Illegal Data Value

The query Function/Subfunction Code is unsupported; query read
of more than 125 registers; query preset of more than 100 registers

A register referenced in the data block does not support queried
read/write; query preset of a subset of a numerical register group.

A preset register data block contains an incorrect number of bytes
or one or more data values out of range.

COMMUNICATIONS HARDWARE REQUIREMENTS

The BE1-851 RS-485 physical interface is three positions of a terminal strip with locations for
Send/Receive A (A), Send/Receive B (B), and Signal Ground (C). Refer to the BE1-851 Instruction
Manual (9289900990) for further details.

DETAILED MESSAGE QUERY AND RESPONSE

A detailed description of BE1-851 supported message queries and responses is provided in the following
paragraphs.

Read Holding Registers

Query

This query message requests a register or block of registers to be read. The data block contains the
starting register address and the quantity of registers to be read. A register address of N will read holding
register N+1. If the query is a broadcast (device address = 0), no response message is returned.

Device Address
Function Code = 03 (hex)
Starting Address Hi
Starting Address Lo

No. of Registers Hi
No. of Registers Lo
CRC Hi error check
CRC Lo error check

The number of registers cannot exceed 125 without causing an error response with the exception code
for an illegal function.

Response

The response message contains the data queried. The data block contains the block length in bytes
followed by the data (one Data Hi byte and one Data Lo byte) for each requested register.

Reading an unassigned holding register returns a value of zero.
Device Address

Function Code = 03 (hex)
Byte Count
Data Hi (For each requested register, there is one Data Hi and one Data Lo.)

9289900992 Rev F BE1-851 Modbus™ Protocol 1-3

Data Lo
Data Hi
Data Lo
CRC Hi error check
CRC Lo error check

Return Query Data

This query contains data to be returned (looped back) in the response. The response and query
messages should be identical. If the query is a broadcast (device address = 0), no response message is
returned.

Device Address
Function Code = 08 (hex)
Subfunction Hi = 00 (hex)
Subfunction Lo = 00 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check

Restart Communications Option

This query causes the remote communications function of the BE1-851 to restart, terminating an active
listen only mode of operation. No effect is made upon primary relay operations. Only the remote
communications function is affected. If the query is a broadcast (device address = 0), no response
message is returned.

If the BE1-851 receives this query while in the listen only mode, no response message is generated.
Otherwise, a response message identical to the query message is transmitted prior to the
communications restart.

Device Address
Function Code = 08 (hex )
Subfunction Hi = 00 (hex)
Subfunction Lo = 01 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check

Listen Only Mode

This query forces the addressed BE1-851 to the listen only mode for Modbus™ communications, isolating
it from other devices on the network. No responses are returned.

While in the Listen Only mode, the BE1-851 continues to monitor all queries. The BE1-851 does not
respond to any other query until the listen only mode is removed. All write requests with a query to Preset
Multiple Registers (Function Code = 16) are also ignored. When the BE1-851 receives the restart
communications query, the Listen Only mode is removed.

Device Address
Function Code = 08 (hex)
Subfunction Hi = 00 (hex)
Subfunction Lo = 04 (hex)
Data Hi = xx (don't care)
Data Lo = xx (don't care)
CRC Hi error check
CRC Lo error check

1-4 BE1-851 Modbus™ Protocol 9289900992 Rev F

Preset Multiple Registers

A preset multiple registers query could address multiple registers in one slave or multiple slaves. If the
query is a broadcast (device address = 0), no response message is returned.

Query

A Preset Multiple Register query message requests a register or block of registers to be written. The data
block contains the starting address and the quantity of registers to be written, followed by the Data Block
byte count and data. The BE1-851 will perform the write when the device address is the same as the
BE1-851 remote address or when the device address is 0. A device address is 0 for a broadcast query.

A register address of N will write Holding Register N+1.
Data will cease to be written if any of the following exceptions occur:

• Queries to write to Read only registers result in an error response with Exception Code of “Illegal
Data Address.”

• Queries attempting to write more than 100 registers cause an error response with Exception
Code “Illegal Function.”

• An incorrect Byte Count will result in an error response with Exception Code of “Illegal Data
Value.”

• There are several instances of registers that are grouped together to collectively represent a
single numerical BE1-851 data value (i.e., floating point data and 32-bit integer data). A query to
write a subset of such a register group will result in an error response with Exception Code “Illegal
Data Address.”

• A query to write a not allowed value (out of range) to a register results in an error response with
Exception Code of “Illegal Data Value.”

Device Address
Function Code = 10 (hex)
Starting Address Hi
Starting Address Lo
No. of Registers Hi
No. of Registers Lo
Byte Count
Data Hi
Data Lo
.
.
Data Hi
Data Lo
CRC Hi error check
CRC Lo error check

Response

The response message echoes the starting address and the number of registers. There is no response
message when the query is a broadcast (device address = 0).

Device Address
Function Code = 10 (hex)
Starting Address Hi
Starting Address Lo
No. of Registers Hi
No. of Registers Lo
CRC Hi Error Check
CRC Lo Error Check

Preset Single Register (Write Single Holding Register)

A Preset Single Register query message requests a single register to be written. The BE1-851 will
perform the write when the device address is the same as the BE1-851 remote address.

9289900992 Rev F BE1-851 Modbus™ Protocol 1-5

Query

Data will cease to be written if any of the following exceptions occur:

• Queries to write to Read only registers result in an error response with Exception Code of “Illegal
Data Address.”

• A query to write a value that is not allowed (out of range) to a register results in an error response
with Exception Code of “Illegal Data Value.”

Device Address
Function Code = 06 (hex )
Address Hi
Address Lo
Data Hi
Data Lo
CRC Hi error check
CRC Lo error check

Response

The response message echoes the Query message after the register has been altered.

DATA FORMATS

BE1-851 data varies from one to four bytes in length. Single byte data resides in the holding register
least-significant byte with the most-significant byte set to zero. Floating-point data and long integer data
(each 32-bits in length) place the two most-significant bytes in the higher holding register address of the
associated register pair.

Floating Point Data Format (FP)

The Modbus™ floating point data format uses two consecutive holding registers to represent a data value.
The first register contains the low-order 16 bits of the following 32-bit format:

• MSB is the sign bit for the floating-point value (0 = positive).

• The next 8 bits are the exponent biased by 127 decimal.

• The 23 LSBs comprise the normalized mantissa. The most-significant bit of the mantissa is always

assumed to be 1 and is not explicitly stored, yielding an effective precision of 24 bits.

The value of the floating-point number is obtained by multiplying the binary mantissa times two raised to
the power of the unbiased exponent. The assumed bit of the binary mantissa has the value of 1.0, with
the remaining 23 bits providing a fractional value. Table 1-3 shows the floating-point format.

Table 1-3. Floating Point Format

Sign Exponent + 127 Mantissa

1 bit 8 bits 23 bits

The floating-point format allows for values ranging from approximately 8.43X10
point value of all zeroes is the value zero. A floating-point value of all ones (not a number) signifies a
value currently not applicable or disabled.

Example
will read from two consecutive holding registers as follows:

: The value 95,800 represented in floating point format is hexadecimal 47BB1C00. This number

-37

to 3.38X1038. A floating-

Holding Register
K (Hi Byte) hex 1C
K (Lo Byte) hex 00
K+1 (Hi Byte) hex 47
K+1 (Lo Byte) hex BB

The same byte alignments are required to write.

1-6 BE1-851 Modbus™ Protocol 9289900992 Rev F

Value

Double Precision Data Format (DP)

The legacy version of BE1-851 Modbus™ supports the double precision data format, which uses two
consecutive registers to represent a data value. The first register (A) contains the high-order 16 bits of
double precision data, and is the actual data value divided by 10,000.

The second register (B) contains the low-order 16 bits of double precision data, and is the actual data

∗

value plus 10,000. The format is: Double Precision = (A
Example

hexadecimal 000916A8. This number will read from two consecutive holding registers as follows:

Holding Register
K (Hi Byte) hex 00
K (Lo Byte) hex 09
K+1 (Hi Byte) hex 16
K+1 (Lo Byte) hex A8

The same byte alignments are required to write.

Long Integer Data Format (LI)

The Modbus™ long integer data format uses two consecutive holding registers to represent a 32-bit data
value. The first register contains the low-order 16 bits and the second register contains the high-order 16
bits.

Example
will read from two consecutive holding registers as follows:

Holding Register
K (Hi Byte) hex 76
K (Lo Byte) hex 38
K+1 (Hi Byte) hex 00
K+1 (Lo Byte) hex 01

The same byte alignments are required to write.

: The value 95,800 represented in double precision format is: 95800 = (9 ∗ 10,000) + 5,800, or

Value

: The value 95,800 represented in long integer format is hex adecimal 0x00017638. This number

Value

10,000) + B.

Integer Data Format (INT)

The Modbus™ integer data format uses a single holding register to represent a 16-bit data value.
Example

from a holding register as follows:
Holding Register

K (Hi Byte) hex 12
K (Lo Byte) hex 34

The same byte alignments are required to write.

Short Integer Data Format (SI)

The Modbus™ short integer data format uses a single holding register to represent an 8 bit data value.
The holding register high byte will always be zero.

Example
from a holding register as follows:

Holding Register
K (Hi Byte) hex 00

K (Lo Byte) hex 84
The same byte alignments are required to write.

9289900992 Rev F BE1-851 Modbus™ Protocol 1-7

: The value 4660 represented in integer format is hexadecimal 0x1234. This number will read

Value

: The value 132 represented in short integer format is hexadecimal 0x84. This number will read

Value

ASCII Character Data Format (ASC (1))

The Modbus™ ASCII character data format uses a single holding register to represent a single character
value. The holding register high byte will always be zero with the ASCII character code in the low byte.

Example

: The character ‘D’ represented in ASCII character format is hexadecimal 44. This number will

read from a holding register as follows:

Holding Register

Value
K (Hi Byte) hex 00
K (Lo Byte) hex 44

The same byte alignments are required to write.

ASCII String Data Format (ASC (x))

The Modbus™ ASCII string data format uses one or more holding registers to represent a sequence or
string, of character values. If the string contains a single character, the holding register high byte will
contain the ASCII character code and the low byte will be zero.

Example

: The string “PASSWORD” represented in ASCII string format will read as follows:

Holding Register

Value
K (Hi Byte) ‘P’
K (Lo Byte) ‘A’
K+1 (Hi Byte) ‘S’
K+1 (Lo Byte) ‘S’
K+2 (Hi Byte) ‘W’
K+2 (Lo Byte) ‘O’
K+3 (Hi Byte) ‘R’
K+3 (Lo Byte) ‘D’

Example

: If the above string is changed to “P,” the new string will read as follows:

Holding Register

Value
K (Hi Byte) ‘P’
K (Lo Byte) hex 00
K+1 (Hi Byte) hex 00
K+1 (Lo Byte) hex 00
K+2 (Hi Byte) hex 00
K+2 (Lo Byte) hex 00
K+3 (Hi Byte) hex 00
K+3 (Lo Byte) hex 00

The same byte alignments are required to write.

Bit Mapped Data Format (BM (x))

The bit mapped data format uses two or more holding registers to represent a sequence of bit values.
The Modbus™ Bit Map data format can represent an 8 bit, 16 bit, 32 bit, or 64 bit value.

Example

: The Bit Map value of the hexadecimal number 0x123456789ABCDEF0 using a BM64 format

will read as follows:

Holding Register

Value
K (Hi Byte) 0x12
K (Lo Byte) 0x34
K+1 (Hi Byte) 0x56
K+1 (Lo Byte) 0x78
K+2 (Hi Byte) 0x9A

1-8 BE1-851 Modbus™ Protocol 9289900992 Rev F

K+2 (Lo Byte) 0xBC
K+3 (Hi Byte) 0xDE
K+3 (Lo Byte) 0xF0

CRC Error Check

This field contains a two-byte CRC value for transmission error detection. The master first calculates the
CRC and appends it to the query message. The BE1-851 recalculates the CRC value for the received
query and performs a comparison to the query CRC value to determine if a transmission error has
occurred. If so, no response message is generated. If no transmission error has occurred, the slave
calculates a new CRC value for the response message and appends it to the message for transmission.

The CRC calculation is performed using all bytes of the device address, function code, and data block
fields. A 16-bit CRC-register is initialized to all 1's. Then each eight-bit byte of the message is used in the
following algorithm.

First, exclusive-OR the message byte with the low-order byte of the CRC-register. The result, stored in
the CRC-register, will then be right-shifted eight times. The CRC-register MSB is zero-filled with each
shift. After each shift, the CRC-register LSB is examined. If the LSB IS a 1, the CRC-register is then
exclusive-ORed with the fixed polynomial value A001 (hex) prior to the next shift. Once all bytes of the
message have undergone the above algorithm, the CRC-register will contain the message CRC value to
be placed in the error check field.

Session Access Registers

The ACCESS REQUEST and the EXIT registers are used to access and release write privileges while
changing relay settings, resetting report registers or using control commands through the Modbus™ port.
This feature is important because it prevents changes from being made concurrently from two areas. For
example, a user cannot make changes from COM 0 at the same time a remote user is making changes
via Modbus™ from COM 2.

Changing the settings through the Modbus™ port requires that the operator write to the ACCESS
REQUEST register to obtain programming access. This must follow writing the ACCESS PASSWORD
register(s) with a password to obtain access to change settings associated with the password. Different
passwords give the ability or access to perform different operations. The relay will deny access if an
invalid password is entered or if another user has already been granted programming access through
another serial port or at the front panel. Only one user can have access at any one time.

If no password protection is used, it is still necessary to obtain access in order to protect against
accidental changes. If password protection is disabled, then writing the ACCESS REQUEST register will
be accepted in place of a password. The relay will transmit a valid response message if the access query
was received and executed. The relay will respond with an error message if the access query could not
be executed.

Changing settings through a Modbus™ communication port consists of the following sequence:

1. Preset Multiple Registers query to ACCESS PASSWORD register(s) to specify password.

2. Preset Multiple Registers query to ACCESS REQUEST register to access write privileges.

3. Preset Multiple Registers queries to change the current settings.

4. Preset Multiple Registers query to EXIT register to clear access and save.

Changes are not made to the working settings but to a scratch-pad copy of the settings. After the
change(s) are made, the new data will be copied to the working settings and saved to non-volatile
memory when the EXIT register is written with a ‘Y.’ It is important to make all changes to relay
parameters before writing the EXIT register. This prevents a partial or incomplete protection scheme from
being implemented.

Template Registers

The BE1-851 uses three templates. A template is a block of holding registers to which the user assigns
one of a number of similar groups of parameters. Templates are used for settings groups, fault
summaries, and report generation. Modbus™ Template Registers 40036 (Settings Group Selection),
40038 (Fault Number Selection), 40039 (Report Selection), and 40040 (Report Focus) DO NOT
REQUIRE any Write Password Access level before they can be written to.

9289900992 Rev F BE1-851 Modbus™ Protocol 1-9

The BE1-851 has four settings groups. The GRP temp late is assigned the parameters of a settings group.
Therefore, before reading or writing settings group values, a user must first specify which settings group is
to be associated with the template. This is accomplished by writing the desired settings group number (0 -

3) into the SETTINGS GROUP SELECTION Template holding register.
The BE1-851 can store up to 16 faults. Each fault is accessed by its fault number, which ranges from 1 to

255. The FLT template is assigned the parameters of a particular fault occurrence. Therefore, before
reading fault summary values, a user must first specify which fault number is to be associated with the
template. This is accomplished by writing the desired fault number (1 - 255) into the FAULT SELECTION
Template holding register.

The BE1-851 generates 10 ASCII reports. The RPT templa te is assigned the text of a report. Therefore,
before reading report text, a user must first specify which report is to be associated with the template. This
is accomplished by writing the desired report number into the REPORT SELECTION Template holding
register along with the associated report identifier, if any, into the REPORT FOCUS Template holding
register.

Fault Summary Registers

The user can enter any fault number (1 - 255) into the FAULT SELECTION Template holding register to
associate summary parameters for that fault number with the FLT Template. The Fault Template Status
register (47513) indicates whether that fault number specifies a recent fault (one of 16 stored faults). If so,
the Fault Template Status register value is the fault number; otherwise, it is zero and all FLT template
values will read zero.

The Fault Indicator register (47512) value is the fault number (1 - 255) of the most recent fault. The user
may construct his front-end GUI to link this register value into the FAULT SELECTION Template holding
register, thereby automatically associating the FLT template with the most recent fault occurrence.

Report Generation Registers

The BE1-851 generates numerous ASCII reports available via serial commands. Several of these reports
are available intact via the Modbus™ communication port. The desired report is first specified by writing
the REPORT SELECTION holding register. If the report requires a number to be specified, such as a fault
number or number of events, that number is written into the REPORT FOCUS holding register. The report
is then available via the RPT template. The report can be read from 1 to 125 registers at a time, with each
register containing 2 ASCII characters of information. The report read queries could be interspersed
among other query types. The RPT template is continually re-read until the report has completed. Once
the report is complete, reading from the RPT template will continually return the ASCII character code of
127 (“7F” hexadecimal). The report cannot be re-read or another report read until the REPORT
SELECTION holding register is re-written.

Contiguous Poll Block Registers

The user may allocate up to 125 holding registers to the Contiguous Poll Block (49875-999). This
allocation allows dispersed registers, which are frequently read to be polled via a single read query. A
register is assigned to a position in the Poll Block by writing its address value into the corresponding
position in the Contiguous Poll Block Assignments registers (40746-870). Writing a zero value leaves that
Poll Block position unassigned. Once assignments are made, the values of the assigned registers may be
read by polling the Contiguous Poll Block. Polling an unassigned position will return a value of zero.

For example, if you wanted to continuously monitor the Date (47364), Time (47365-66), Fault Indicator
(47512) and Breaker Status (47388) Holding Registers, you would first configure the Contiguous Poll
Block Registers by writing the desired register address values 7364, 7365, 7366, 7512 and 7388 into the
Contiguous Poll Block Assignment registers 40746 through 40750, respectively. You may now begin
monitoring the specified registers by reading the first 5 locations in the Contiguous Poll Block; i.e., reading
register 49875 for the Date (as specified in it’s corresponding assignment register 40746), reading
register 49876 and 77 for the Time (as specified in their corresponding assignment registers 40747 and

48), reading register 49878 for the Fault Indicator (as specified in it’s corresponding assignment register

40749) and reading register 49879 for the Breaker Status (as specified in it’s corresponding assignment
register 40750).

Exception Code Enhancement Registers

When a BE1-851 responds to a Preset Multiple Register query with an error response message,
additional information detailing the cause of the error may be available in the ERROR DETAILS block of

1-10 BE1-851 Modbus™ Protocol 9289900992 Rev F

holding registers (49835-54). The information is in ASCII format and available by reading the message
string from the ERROR DETAILS block. The message remains available until the next Preset Multiple
Register query is executed unless that query is to the FAULT SELECTION Template holding register.
Since this register can be written automatically and randomly in time, the ERROR DETAILS block will not
be updated.

The ERROR DETAILS block will also contain the exit status following a Preset Multiple Register query to
the EXIT (40001) register. You may clear the ERROR DETAILS message at any time without affecting
system operation by sending a Preset Multiple Register query to any unassigned holding register.

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1-12 BE1-851 Modbus™ Protocol 9289900992 Rev F

SECTION 2 • REGISTER TABLE

MAPPING BE1-851 PARAMETERS INTO MODICON HOLDING REGISTER ADDRESS SPACE

General

Parameters are mapped into the holding register address space (40001 - 49999) in blocks according to
access type.

Any Holding Register not listed in the Register Table is an unassigned Holding Register. A value of zero
always results when reading an unassigned Holding Register. Writes to unassigned Holding Registers
are legal, but no action will be taken (the write is ignored).

Conventions

The Data Format column uses the following abbreviations:
ASC(x) - ASCII string, where x = the maximum defined string length

BM(x) - Bit-map, where x = the number of related bits
FP - Floating point
INT - Integer (16-bit integer)
LI - Long Integer (32-bit integer)
SI - Short Integer (8-bit integer)
DP - Double Precision (legacy BE1-851 only)

The Notes column uses the following abbreviations:
GRP - Group Template Member

FLT - Fault Template Member
RPT - Report Template Member
NS - Not Supported
TS - Time Stamp format: MSEC of the day (0 to 86,400,000 ms) and days since 01/01/1984.
LEG - Original (legacy) BE1-851 Modbus™ parameter mapping.
PS - Effective only when the Password Security parameter is enabled. See REGISTER DETAILS for

Password Security holding register 40989.

PW - Effective for any communication port active with ASCII protocol and for the Modbus™ port

(COM 2) when Password Security is enabled.

9289900992 Rev F BE1-851 Modbus™ Protocol 2-1