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.5
November 21, 2008
1.1.3.3 GLS Select Discrete output
This contact is closed to ground when the ILS/GLS Source Select Discrete input is set to "GLS", and is
opened otherwise. The return current path is through the chassis ground. This output is intended for
activating an external indicator and reacts within one second.
1.1.3.4 Approach Tuned Discrete output
This contact is closed to ground when a valid approach is selected, and is opened otherwise. The
return current path is through the chassis ground. The state will toggle during Self-Test mode and
during the Guidance Test. This output reacts within one second. It is intended for simulating the “Loc
Tune” output of the ILS to indicate that the ILS is properly tuned to the base station.
1.1.3.5 Approach Available Discrete output
This contact is closed to ground when the Approach Tuned Discrete contact is closed to ground and
the Five-Minute Look-Ahead SBAS Integrity limits are below the alert limits for LPV or LP approaches.
The contact is opened otherwise. The return current path is through the chassis ground. The state will
toggle during Self-Test mode and during the Guidance Test.
The 'Approach Available' state is also reported via the ARINC 429 Approach Selection Status output
data label.
1.1.3.6 System Valid Discrete output
This contact is closed to ground during normal operation, and is opened when the GLSSU is non
operational (in Fault mode). The return current is through the chassis ground. The state will toggle
during Self-Test mode and during the Guidance Test.
1.1.3.7 Discrete Output Return pins
These pins (J3-9, J3-10) are connected internally to the GLSSU case and to the chassis ground pins,
J1-33 and J3-3. They may be used to provide a return current path from the discrete outputs.
1.2 ARINC 429 INTERFACES
1.2.1 ARINC 419/429 DATA INTERFACE STRUCTURES
The GLSSU uses ARINC 429/419 data interface busses. An ARINC word is a 32-bit entity, which
decomposes into the following fields. Bit 32 is MSB, bit 1 is LSB and is output first in time:
PARITY
SIGN STATUS
MATRIX (SSM)
DATA
SOURCE
DESTINATION
INDICATOR (SDI)
LABEL ID
(OCT)
32 31-30 29-N 10-9 8-1
The Label Id field is used to uniquely identify the data words. It ranges from 0 to 377 octal. The labels
used / outputted by the GLSSU are detailed below. Other labels are ignored / not outputted by the
GLSSU.
The Parity bit is odd (odd number of "ones") on all incoming and outgoing labels. Input data words
received with a parity bit error are ignored.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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