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Revision A5
HXr Installation Manual GRT Avionics
Section 5: Equipment Interconnect Details
5.1 Serial Ports
The GRT Horizon HXr has 8 high speed serial ports. Pinout diagrams are available in the Appendix
of this manual. Check the website, www.grtavionics.com, for periodic updates as capabilities are
added to the system.
Each serial port has a user-definable assignment and baud rate so the EFIS may be configured to
the equipment attached to it. The connector diagrams in the Appendix of this manual and on the
website provide general suggestions for serial port assignment. You may use any serial port with
baud rates compatible with the equipment connected to it. Note that the baud rate for a port is
the rate for both input and output. Detailed instructions for configuring serial ports are in the HXr
Set-Up Guide and Equipment Supplements.
5.2 Inter-Display Link
Display units communicate via ethernet cable so that most entries made during flight can be made
from any display unit, and will be applied to all. The data that is transmitted on the Inter-Display
Link is user-defined (Set Menu, General Setup, Inter-Display Link). It is best to design the system
to allow devices to communicate directly to multiple screens for redundancy, but the number of
serial ports available may limit this. Data may also be shared via the Inter-Display Unit Link, which
allows the serial ports to be used for more devices. If more than two HXr displays are connected,
it is necessary to use an ethernet hub.
5.3 ARINC 429
All Horizon HXr units have a built-in ARINC module independent of the eight serial ports. GRT
Horizon uses of ARINC include control of an autopilot using GPSS/GPSV mode, accepting TIS
information from a GTX 330 transponder, and exchange of information with GPS and Nav receivers
The connections are made via 9-pin D-Sub, designated Connector C.
The ARINC 429 connection provides 2 serial inputs and 1 serial output that conform to the ARINC
429 serial communication standard. The inputs may be configured for various uses according to
the equipment installed in the airplane.
5.4 Analog Input
The GRT HXr has eight user-configurable analog inputs. Similar to the serial ports, the analog inputs
may be configured to fit the attached equipment. Common uses include such items as flap and
trim position indicators, although any 0-12 volt signal may be displayed.
5.5 Discrete Output
Six discrete outputs are provided which can be configured to provide an open/ground to control
external indicators or other devices. These outputs can control 0.5 amps individually, with a
