36
9 Available protection settings
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10 Modbus communication port register map
A ModbusRTU communication module is integrated to the trip unit for certain styles.
10.1 Viewing/setting Modbus parameters
Modbus connection parameters can be viewed and set from LCD display, via PXPM and
Modbus communication. To view from Modbus communication, the settings are stored
beginning at register number 404000 and extending through 404003 and may be read by
using function code 03 or 04, listed in the following table. These four registers can be
written one by one with function code 06 to change Modbus setting. If the data written into
these registers is out of range, it will result in an exception code 03.
Definition
modbus register number
Data range
Slave ID
404000
001 – 246 (factory default = 2)
Baud rate
404001
00 = 9600 bit/s
01 = 19200 bit/s (factory default) 02 = 38400 bit/s
03 = 57600 bit/s
Parity
404002
00 = None
01 = Odd
02 = Even (factory default)
Stop bit
404003
00 = 1 bit (factory default)
01 = 2 bits
10.2 Communication protocol
Only the Modbus RTU communication mode is recognized by the trip unit. The trip unit can
support a maximum of 122 registers (244 data bytes) in a single Modbus transaction. The
trip unit responds to Modbus function codes 02, 03, 04, 06, 08 and 16.
10.3 Modbus register map
10.3.1 Input status (discrete inputs)
Input status bits 101001 through 101032 may be available using function code 02. The status
definitions are defined the following table. The first 16 bits are the actual status state while
the late 16 bits indicate whether the corresponding status state is valid, or supported by the
trip unit.
input
Definition
input
Definition
1001
Breaker is in the closed position
1017
Breaker is in the closed position is valid
1002
Un-acknowledged trip condition
1018
Un-acknowledged trip condition is valid
1003
Active or un-acknowledged alarm
1019
Active or un-acknowledged alarm is valid
1005
Maintenance mode is active
1021
Maintenance mode is active is valid
1006
Test mode is active
1022
Test mode is active is valid
1010
Long delay pickup is active
1026
Long delay pickup is active is valid
1011
Zone interlock is active
1027
Zone interlock is active is valid
1013
“Ground” is source ground
1029
“Ground” is source ground is valid
10.3.2 Real-time data object registers
The data changing in real time, such as current, voltage, power, etc. are shown in the table
below. Real time data can be obtained either in IEEE floating point or in fixed point format.
For data shown in fixed point format, each result would be the real time data multiplied by
a scale factor. The scale factors are shown as the last column in the table. Energy objects
can be only obtained in fixed point format.
Each data object occupies two registers (four bytes) in length except for certain energy
objects. These energy objects occupy four registers. Since these objects have the capability
to change in real time, a complete data object must be obtained in a single transaction to
avoid data tearing. Attempting to access a partial data object will result in an exception code
84. Refer to a later section entitled “Exception codes”.