GPS 155Xl/GNC 300XL Installation Manual
P/N 190-00067-22 Rev E Page 4-10
4.4.5
Communications Loopback Test
This page displays the results of communication loopback tests. Three channels are tested: RS232 channels 1 and 2,
and ARINC 429. Results of the test are either "OPEN" or "OK." Open means the channel’s transmitter and receiver
are not connected or the test failed. The tests are performed continuously while on this page except for RS232
channel 2 (this channel is only tested at power on and the results are displayed on this page). Therefore, the unit
must be turned off and the receiver/transmitter connected or disconnected. Then turn the unit on to perform the test.
To test the channels:
•
RS232 channel 1—Connect RS232 channel 1 receiver and transmitter
•
RS232 channel 2—Connect RS232 channel 2 receiver and transmitter
•
ARINC 429—Connect ARINC 429 receiver and transmitter
4.4.6
Altitude Input Test
Select the Gray Code Altitude Test Page if this input is used. Verify that the altitude input is reading the correct
altitude. NOTE: This does not display serial altitude.
4.4.7
OBI Test
Select the OBI Test Page. Using the controls on the GPS 155XL/GNC 300XL front panel, make the selections
indicated below and verify the interfaces as appropriate:
OBI Data
VALID—Ensure that the OBI indicates the proper value
INVALID—Ensure the OBI is invalid
OBI Value—Ensure that the OBI displays the value entered when the VALID option is selected
NOTE:
The 3 lines that make up the OBI interface may be toggled individually. This may be done
from the "Value" field. Cycle this field to the desired line (either CLOCK, DATA, or SYNC)
and toggle the output to HIGH or LOW.
4.4.8
Signal Acquisition Test
Following normal power-up, the Self Test Page will be displayed followed by the Data Base Page. Upon approval of
the Data Base Page, the Satellite Status Page will be displayed. If the unit is unable to acquire satellites, relocate the
aircraft away from obstructions which might be shading reception. If the situation does not improve, check the
antenna installation.
Once GPS position information is available, use the DIRECT-TO key to activate the navigation function to a nearby
NAVAID, intersection, or airport. Ensure any connected equipment is transmitting data to and/or is receiving data
from the GPS 155XL/GNC 300XL and is functioning properly (see the Pilot's Guide for more information on the
DIRECT-TO function).
