Slave response, Bytes, Example – GE Industrial Solutions EntelliGuard TU Trip Units User Manual

Page 63: Description, Slave address, Message from slave 17, Function code, Store setpoints, Data starting address, 04 5c

DEH-4567B

EntelliGuard TU Trip Units: UL/ANSI Models

Serial Communication

Slave Response

Bytes Example

Description

Slave Address

message from

slave 17

Function Code

store setpoints

Data Starting
Address

04 5C

setpoint address

04 5C

Number of
Setpoints

00 02

2 setpoints

CRC

82 7A

CRC error code

Function Code 20H

Modbus Implementation:
Read File Record

This command allows the master to read a file containing
the full 255 events and analog RMS data. All Request Data
Lengths are provided in terms of number of bytes and all
Record Lengths are provided in terms of registers.

Table 8-7: Modbus Packet Format for Function Code 20

Master
Transmission

Bytes

Value

Slave Address

1 - 245

Function Code

0x14

Byte Count

0x07 to 0xF5

Reference Type

File Number

0x0001 (Read all 255 Events)

0x0002 (Read Current RMS)

Record Number

0x 0000 to 0x03E8

0x0000 to 0 x 007B

ERROR RESPONSES

When an EntelliGuard Trip Unit detects an error other than
a CRC error, a response will be sent to the master. The
MSBit of the FUNCTION CODE byte will be set to 1 (i.e. the
function code sent from the slave will be equal to the
function code sent from the master plus 128). The
following byte will be an exception code indicating the type
of error that occurred. Transmissions received from the
master with CRC errors will be

ignored by the EntelliGuard

Trip Unit.

The slave response to an error (other than CRC error) will
be:

Table 8-8: Slave Responses to Errors

Slave Address:

1 byte

Function Code

1 byte (with MSbit set to 1)
Exception

Code

1 byte

Crc:

2 bytes

The EntelliGuard Trip Unit implements the following
exception response codes:

• 01 - Illegal Function:

The function code transmitted is not one of the
functions supported by the EntelliGuard Trip Unit..

• 02 - Illegal Data Address:

The address referenced in the data field transmitted by
the master is not an allowable address for the
EntelliGuard Trip Unit.

• 03 - Illegal Data Value:

The value referenced in the data field transmitted by the
master is not within range for the selected data
address.

MODBUS REGISTER MAP
• Function Code 02 – Read Input Status
• Function Code 03 - Read Holding Registers
• Function Code 04 – Read Input Registers
• Function Code 05 – Force Single Coil
• Function Code 06 - Preset Single Holding Register
• Function Code 16 Write Multiple Holding Registers
See appendix C for the full register map.

PRACTICAL MODBUS SETUP

This section is intended to give you a quick and simple
checklist to run through when commissioning an
EntelliGuard Trip Unit on a Modbus Network. The goal is to
give you some concrete steps to get your device up and
running quickly by eliminating some of the guesswork.

Step 1: Set up the Serial Port on the Master Device

If your computer does not have a built-in 9 pin serial

port, you will have to attach a USB-to-serial adapter.
These devices are readily available at most office supply
stores or online. For best results, buy a name brand. Be
sure to install the driver software that comes with the
device.

Once the serial port hardware is enabled on the

computer, determine which “logical port” (COM1, COM2,
etc.) the computer has assigned to the port you plan to
use. This information is available in the “Device
Manager” function of Windows. Consult the web or your
computer’s help facility for information on how to
access the Device Manager.

The Device Manager will display information similar to
what you see below. The serial ports are listed under the
heading “Ports (COM & LPT).”