039 Multiplexores y Demultiplexores

MULTIPLEXORES Y DEMULTIPLEXORES

• MULTIPLEXORES (MUX):• Un Multiplexor es un dispositivo que tiene varias entradas de datos, una única

salida y varias entradas de selección.• El dato o datos que vamos a obtener a la salida depende de la entrada que

seleccionemos desde las entradas de selección.• Los MUX son circuitos combinacionales que pueden ser fácilmente implementados

con compuertas lógicas AND, OR y NOT.• Ejemplo de un MUX con dos entradas, una salida y una entrada de selección:

•


• MULTIPLEXORES (MUX):• Multiplexor de 4 entradas de datos, dos entradas de selección y una salida.

MULTIPLEXORES Y DEMULTIPLEXORESLa ecuación Booleana de un MUX de 4 a 1 entrada es:

MULTIPLEXORES Y DEMULTIPLEXORESImplementación de un MUX de 4 a 1 con compuertas lógicas:

MULTIPLEXORES Y DEMULTIPLEXORESImplementación de un MUX de 4 a 1 utilizando un decodificador de 2 a 4 líneas:




• DEMULTIPLEXORES (DEMUX):• Básicamente son lo contrario de los multiplexores; es decir, tienen una sola

entrada de datos y múltiples señales de salida. Los datos de entrada se copiarán en la salida que corresponda de acuerdo a las entradas de selección.

• Un Demultiplexor es un circuito igualmente combinacional que posee:– 1 entrada de información.– n entradas de selección.– 2^n salidas de información.


• Tabla de la verdad de un DEMUX de 1 a 4 salidas.



• Veamos un ejemplo basado en los sistemas de entretenimiento de cabina.• La tripulación técnica y los TCP desde sus paneles de control y una vez que los sistemas de

reproducción adecuados están en funcionamiento, se envían señales de audio de música y sonido de películas que llegan a los paneles de distribución del asiento de cada pasajero. Cada butaca tiene un punto para enchufar la clavija de un juego de auriculares, además de un interruptor-selector multicanal, un interruptor de mando de luces y un timbre para llamar a la azafata.


• Veamos un ejemplo basado en los sistemas de entretenimiento de cabina.• Estos equipos disponen de un sistema de sobre-mando (“override”) desde el panel

de control de los TCP o desde la cabina de pilotos, de modo que la tripulación auxiliar de cabina, o uno de los pilotos, pueda interrumpir la audición a fin de que los pasajeros puedan escuchar los avisos de la tripulación a través de los auriculares.


• Veamos un ejemplo basado en los sistemas de entretenimiento de cabina.• Si se tuvieran que usar métodos eléctricos convencionales para la interconexión de

todos los elementos que constituyen el sistema, se necesitaría una considerable cantidad de cables y conectores.

• Para ello las señales de audio se transmiten en formato digital y en modo de multiplexado por medio de un transmisor de datos que consiste en un solo cable coaxial.

MULTIPLEXORES Y DEMULTIPLEXORESThe Passenger Address (PA) and entertainment system comprises the following basic functions:

- Passenger Entertainment System (PES),- PES video,- PRerecorded Announcements and Music system (PRAM).The PES comprises the PES music, the PA announcement and the passenger service.

MULTIPLEXORES Y DEMULTIPLEXORES• The PES transmits prerecorded music programs, PA information, video and video sounds

to the passengers.• The audio signals can be heard through headphones connected to the Passenger Control

Units (PCUs).• The PCU allows several music channels and video audio channels to be selected and the

volume to be adjusted. The PCU also allows the reading lights and passenger calls to be remotely controlled through the Passenger Services System (PSS).

MULTIPLEXORES Y DEMULTIPLEXORES• The PES audio reproducers supply music channels to the MAIN MUltipleXer (MAIN MUX)

and BoardinG Music (BGM) channels to the CIDS directors (DIRs). The CIDS broadcasts the BGM through the loudspeakers. BGM channel and volume control is performed on the

Flight or Forward Attendant Panel (FAP).• The MAIN MUX is connected to the CFDS via the CIDS DIRECTOR to ensure the PA BITE

function.

MULTIPLEXORES Y DEMULTIPLEXORES• The PES video shows prerecorded video movies and video announcements through

different Display Units (DUs) in the passenger compartment.The video is transmitted to the video System Control Unit (SCU) from the Video Tape Reproducers (VTRs).• The video sound is transmitted to the MAIN MUX and to the CIDS. Therefore video sounds

can be heard from the headset through the PCU or from the loudspeakers. The in-seat video DUs are supplied through the MAIN MUX.

MULTIPLEXORES Y DEMULTIPLEXORES• The PRAM can be:

- an audio tape reproducer,- a compact disc reproducer,- a flash card directly plugged in the Flight Attendant Panel only.• Reproducers or flash card contain prerecorded announcements and BGM supplied to

the CIDS DIRs. The announcements are also sent to the MAIN MUX. The PRAM is controlled from the FAP.

MULTIPLEXORES Y DEMULTIPLEXORES• The PRAM can be:

- an audio tape reproducer,- a compact disc reproducer,- a flash card directly plugged in the Flight Attendant Panel only.• Reproducers or flash card contain prerecorded announcements and BGM supplied to

the CIDS DIRs. The announcements are also sent to the MAIN MUX. The PRAM is controlled from the FAP.

MULTIPLEXORES Y DEMULTIPLEXORES• The MAIN MUltipleXer generates a Radio Frequency (RF) signal which contains

the audio information from the audio reproducer(s), and video System Control Unit (SCU), Passenger Address (PA) announcements from the Cabin intercommunication Data System (CIDS) and video signals from the video SCU.

• If PA announcements are to be made, the CIDS sends a keyline signal to the audio reproducer and to the Video Tape Reproducers (VTRs) , through video SCU, to stop them

MULTIPLEXORES Y DEMULTIPLEXORES• A coaxial cable transmits the RF signal to the Seat Electronic Boxes (SEBs),

through the Wall Disconnect Boxes (WDBs). The SEBs only transmit the selected audio signal to the headsets through the Passenger Control Unit (PCU)

• Passenger Services System (PSS) digital data is exchanged between the MAIN MUX and the PCU. The MAIN MUX transmits this data through an ARINC 429 data bus to the CIDS directors (DIRs).

MULTIPLEXORES Y DEMULTIPLEXORES• The SEB changes the combined RF audio signal back to its original analog form

and only transmits the selected program to the PCU. Each SEB supplies a maximum of 3 PCUs. The SEBs receive PCU selected data and transmit it to the CIDS DIR, through the WDB and the MAIN MUX.

• The PCU allows the passengers to select the channel, to adjust the volume and to hear music and video sounds

MULTIPLEXORES Y DEMULTIPLEXORESThe audio reproducers provide different music programs from cassettes tape or compact disks, to the MAIN MUX. The audio reproducers also send one music program, among 4 music programs, for BoardinG Music (BGM), to the CIDS DIRs

MULTIPLEXORES Y DEMULTIPLEXORESThe BITE is used for detection and isolation of system and component faults. All BITE data of the Passenger Entertainment System (PES) music is assembled in the MAIN MUX. It transmits the BITE data through an ARINC 429 data bus to the Centralized Fault Display System (CFDS).

MULTIPLEXORES Y DEMULTIPLEXORESThe BITE data transmission to the CFDS is made continuously in normal mode and on request in interactive mode. In interactive mode, the BITE is connected to the MCDU through the CFDS.The MAIN MUX starts an automatic self-test after power-up and a manual self-test after transmission of the related MCDU commands.

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039 Multiplexores y Demultiplexores