9 Modbus RTU – integrated Modbus port specification
9.2 Network communication protocol
PXR Electronic trip unit
01/21 MN012005EN
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9.2 Network communication protocol
•
The release will only recognize the Modbus RTU communication
module.
•
The trip unit is able to support a maximum of 122 registers
(244 data bytes) in a single Modbus transaction.
•
The release will only react to a limited number of Modbus function
codes. These are function codes 02, 03, 04, 06, 08 and 16.
Function codes 03 and 04 are used interchangeably to obtain
register data.
9.3 Modbus register map
•
There are seven different release types in the NZM digital circuit
breaker family. As a result, the devices access the registers
differently, since not all versions support all functions.
•
Release type -AX does not support an internal Modbus connection;
register access is therefore not possible.
•
Release types -VX...-T and -PX...-TZ and -TAZ support the ground-
fault protection function. For these types, the ground-fault setpoints
of group 1 (ground current I
g
) can be accessed in the real-time data.
•
Release types -PX, -PMX and -PX...TZ and -PX...-TAZ support
voltage measurement and are thus equipped for extended
measurement data. For these types, the voltage-related objects
(voltage, power, energy, and the power factor) can be used in the
real-time data.
•
Release type -PX...-TAZ supports the maintenance mode.
For this type, the maintenance mode setpoints can be accessed in
group 0 and in the “Remote Control” group.
