© 2021 Carrier
17
ESTABLISHING COMMUNICATION
The NXTSD507HD and NXTSD512HD screens both use Modbus RTU via RS-485 to connect to the
connected devices. The screen is the master device (client) and the connected devices are the slave devices
(servers). There can be only one master device on a Modbus RTU network so if additional Modbus
connectivity is needed (for building management, etc.), this can be done using the Modbus TCP/IP server
function from the screen. See section
MODBUS TCP/IP SERVER
for additional information on this.
If there is only going to be a single NXF4000 or PPC4000 connected to the NXTSD507HD or
NXTSD512HD, it should simply be connected to serial port 1. This configuration is the default as shipped
and the control will immediately communicate if it is set to the default communication settings. If the unit
is not set for the default communication settings, initiate the device discovery process as outlined for
multiple controls in the
SYSTEM
Options
Miscellaneous
Device Configuration
section. Note that
the only reason the communication settings may have changed is if the control has been installed for some
time and the settings were previously changed for building automation use. If the control is new and
communication isn’t established immediately, first check the wiring.
The NXTSD507HD and NXTSD512HD will automatically discover any connected NXF4000 or PPC4000
controls connected when the device discovery is initiated. It is important that each connected NXF4000 or
PPC4000 has a different unit address when multiple controls are connected. The default unit address of 247
can be retained when there is only one control or if each is connected to a different serial port. The reason
for unique unit addressing is to avoid conflicts.
