CHAPTER 6: COMMUNICATIONS
MODBUS COMMUNICATIONS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
101
to requests issued by a master device. A subset of the Modbus protocol format is
supported that allows extensive monitoring, programming, and control functions using
read and write register commands.
See the D90
Plus
Communications Guide for additional details on the Modbus protocol and
the Modbus memory map.
Modbus protocol
The Modbus server can simultaneously support one client over serial RS485 and four
clients over Ethernet. The server is capable of reporting any indication or measurement
and operating any output present in the device. A user-configurable input and output map
is also implemented.
The D90
Plus
operates as a Modbus slave device only.
Select the
Settings > Communications > Modbus > Protocol
menu item to open the
Modbus protocol configuration window.
Figure 82: Modbus protocol configuration settings
The following Modbus protocol settings are available.
Modbus Slave Address
Range: 1 to 254 in steps of 1
Default: 254
This setting specifies the Modbus slave address for the D90
Plus
. Each device must have a
unique address from 1 to 254. Address 0 is the broadcast address to which all Modbus
slave devices listen. Addresses do not have to be sequential, but no two devices can
have the same address or conflicts resulting in errors will occur. Generally, each device
added to the link should use the next higher address starting at 1.
Modbus TCP Port Number
Range: 1 to 65535 in steps of 1
Default: 502
This setting specifies the Modbus TCP port number for Ethernet communications. Power
to the D90
Plus
must be cycled for changes to this setting to take effect.
Modbus user map
The Modbus user map provides read-only access for up to 256 registers. To obtain a
memory map value, enter the desired address in the
Parameter
field (this value must be
converted from hexadecimal to decimal format). The corresponding value (if programmed)
is displayed in the value field. A value of “0” in subsequent register address lines
automatically returns values for the previous address lines incremented by 1. An address
value of “0” in the initial register means none and values of “0” will be displayed for all
registers. Different address values can be entered as required in any of the register
positions.
Select the
Settings > Communications > Modbus > User Map
menu item to open the
Modbus user map configuration window.