GE Agile P50 Series Technical Manual page 210

12 SCADA Communications
2 SCADA COMMUNICATIONS
2.1 Modbus
This section describes how the MODBUS standard is applied to the Px50 platform. It is not a
description of the standard itself. The level at which this section is written assumes that the reader is
already familiar with the MODBUS standard.
The MODBUS protocol is a master/slave protocol, defined and administered by the MODBUS
Organization. For further information on MODBUS and the protocol specifications please see the
Modbus web site (www.modbus.org).
2.1.1 Overview
2.1.1.1 Physical Connection and Link Layer
Only one option is available for connecting MODBUS.
• Rear serial port 1 - for permanent SCADA connection via EIA(RS)485
The MODBUS interface uses 'RTU' mode communication rather than 'ASCII' mode as this provides
more efficient use of the communication bandwidth. This mode of communication is defined by the
MODBUS standard.
The IED address and baud rate can be selected using the front panel menu or with P50 Agile
configurator.
When using a serial interface, the data format is: 1 start bit, 8 data bits, 1 stop bit (a total of 10 bits per
character).
2.1.2 MODBUS Functions
2.1.2.1 Protocol Mapping
The following MODBUS function codes are supported:
Code
02
03
04
05
16
• Exception Codes generated in case of an error:
Code
01 Illegal Function Code
02 Illegal Data Address
9-4
Function Name
Read Input Status
Read Holding Registers
Read Input Registers
Force Single Coil
Preset Multiple Registers
MODBUS Response Name
Addresses starts with
1x addresses
4x addresses
3x addresses
0x addresses
4x addresses
Product interpretation
The function code received in query is not supported by the IED.
The start address received in the query is not an allowable value.
Note: If the start address received is correct but
the range includes unsupported address,
then this error is produced.
P50 Agile P153
P153/EN M/B