INSTALLATION MANUAL
CMA-5024 GLSSU
This document includes Proprietary Information and shall not be reproduced or communicated to third party
without prior written permission by CMC Electronics Inc.
Page A.2
November 21, 2008
1.1.1 ARINC 429 SOURCE/DESTINATION IDENTIFIER (SDI) DISCRETE INPUTS
These two input discretes identify the installation position of the GLSSU in the aircraft as per the table
below. The GLSSU uses this SDI data for screening the ARINC 429 input data words, and sends the
same SDI data in each data word transmitted on the ARINC 429 output busses.
ARINC Bit 10 ARINC Bit 9 Device
SDI #2 SDI #1 Ident
Open (0) Open (0) Not Used
Open (0) Gnd (1) Unit 1 (Left)
Gnd (1) Open (0) Unit 2 (Right)
Gnd (1) Gnd (1) Unit 3 (Center)
The discrete inputs must be connected locally to the Input Discrete Return on the aircraft connector J1
or J3 for selecting the ground state, or must be left unconnected for selecting the open state. The
GLSSU reads the state of these discrete inputs only at power-up during the Self-Test mode; later state
changes will not be detected.
1.1.1.1 Data Loader Discrete input
The GLSSU reads periodically the state of this discrete input, once per second. Digital filtering ensures
that noise glitches will not cause false indications.
The GLSSU enters the Data Load mode only when this discrete input is set to ground, for maintenance
purposes and using either the ARINC 615 protocol via ARINC 429 or the serial RS232 bus described
later.
1.1.1.2 DADS 419/429 Select Discrete input
The GLSSU reads the DADS 419/429 Select input discrete pin and determine its state as defined
below:
- Discrete pin open indicates a connection to DADS 429.
- Discrete pin at Ground indicates a connection to DADS 419.
The same state applies for the two DADS input ports. The state of this input discrete is determined
only during Self-Test mode; later state changes will not be detected.
1.1.1.3 429 HS/LS Select Discrete input
The GLSSU reads the 429 HS/LS Select Discrete input pin and determine its state as defined below:
- Discrete pin open indicates a high speed GPS ARINC 429 output.
- Discrete pin at Ground indicates a low speed GPS ARINC 429 output.
The same state applies for all GPS ARINC 429 outputs. The state of this input discrete is determined
only during Self-Test mode; later state changes will not be detected.
1.1.2 AIR/GROUND DISCRETE INPUT
The GLSSU reads the Air/Ground discrete input pin and determine its state as defined by the
Air/Ground Discrete Open in Air APD setting. Refer to Appendix E. The GLSSU reacts to changes in
Air/Ground Discrete input within a one second period.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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