Where is it coming from? Airbus A320

[AF330]

Hi everyone,
Just wanted to know where the data was coming from on each ECAM page! Thanks:

ELEC = ?
FUEL = FQI
AIR CONDITIONING/ PACKS = CTC and CPC?
TEMP IN THE CABIN: CTC and CPC? AEVC?
F-CTL = FAC ELAC SEC?
ENG = ECU?
HYDRAULICS= ?

Thanks! ;)

[Gryphon]

From FCOM DSC EIS General 31-05-30

SYSTEM DATA ACQUISITION CONCENTRATOR (SDAC)

The two identical SDACs acquire data, then generate signals. Some of these signals go to the three DMCs, which use them to generate displays of system pages and engines parameters. Others go to the flight warning computers, which use them to generate ECAM messages and aural alerts.

[BOAC]

Pull up a chair and buy some popcorn...............

[AF330]

Thanks Gryphon!
Where is SDAC getting info? Which computers? How are the SDAC powered? Thanks

[spannersatcx]

1. General

This note defines the interfaces between the various aircraft systems and the System Data Acquisition Concentrator (SDAC).

2. Interface

A. Signal Type


The SDAC recopies a certain number of parameters to distribute them to other equipment in digital form (ARINC 429 standard). These parameters, input to the SDAC, are of different types:

- wired discretes


- boolean on bus


- digital on bus


- analog on synchro


- low level DC


- high level DC


- high level AC


- frequencies


- resistances (temperatures)


- supplies and miscellaneous.


Except for supplies and miscellaneous, all these signals are available on the high speed output buses (2 lines of 3 buses)(100 KHz frequency).

Each analog or digital parameter has a corresponding output label - Source Data Identifier (SDI) group.

Each discrete or boolean parameter has a corresponding output label - SDI/bit group.

Each label includes a sign/status matrix (SSM) or bit pair (30,31) which defines the validity of the parameter(s) contained in the label.
(1) Wired discretes


There are two types of wired discretes:

P- (ground or open circuit) or P+ (14 V to 46 V or open circuit).

For these wired discretes P+ and P-, when one input port grouping 16 discretes max (in modules of 4 discretes) is detected failed (monitored by an "exclusive or"), the SSM of the label associated with all booleans of this label is coded FW at the SDAC output:

bits (30,31) = (1,1), after confirmation over 5 cycles.

To keep the positive logic some input discretes are reversed from the electric input state to the boolean output state i.e. :

- For the P- type, the boolean output state is set to 1 when the electrical input state is ground and set to 0 when the electrical input state is open


- For the P+ type, the boolean output state is set to 0 when the electrical input state is 28VDC and set to 1 when the electrical input state is open.

(2) Booleans on bus


Each boolean on a SDAC input bus is recopied as on the output bus. Its validity, represented by the SSM of the output label is the same as at the input for the Normal Operation (NO), the Functional Test (FT), the Failure Warning (FW) and the Not Computed Data (NCD).

However, if a wrong parity or a no refresh is detected on an input label:

- Before confirmation (5 cycles or 500 ms) the data are retransmitted on the output bus with the last valid value and the associated SSM.


- After confirmation, the data are retransmitted on the output bus with the last valid value and the SSM set to FW: bits (30,31) = (1,1).


(3) Analog signals


These are parameters requiring a full label on the output label. However, some of these parameters correspond to specific options and are only recopied on the output buses if the relevant programming pin is validated (connected to ground).

(4) Digital on bus


Each of these parameters acquired by a SDAC input bus uses one label on the output bus. The value to be transmitted requires a certain number of bits of the label which varies from one parameter to the other. Parameters in digital form are repeated on the output bus without undergoing transformation. The parameter keeps its validity at the output (SSM) for the Normal Operation (NO), the Functional Test (FT), the Failure Warning (FW) and the Not Computed Data (NCD).

However, in the event of a wrong parity or a no refresh, the boolean transmission rule applies since the parameters are coded FW:

bits (30,31) = (0,0).
(5) Analog on synchro


These signals correspond to angular information. They require 3 input pins plus one pin for the reference voltage. The transmitted measurement ranges are 0 deg. to 360 deg.

On the output labels corresponding to these parameters, an SSM coded NCD: bit (30,31) = (1,0) indicates an open circuit at the input or the absence of the reference voltage.

(6) Low level DC (LLDC)


These are analog information where the value to be transmitted is materialized on the SDAC input by a proportional voltage on a measurement range which varies according to the parameter. This measurement range is set between 2 values M1 and M2 where :

OV < M2 < M1 < 10V.

(7) High level DC (HLDC)


Similar to the LLDC information but the measurement range is different.

The value to be transmitted on the output bus is proportional to the input voltage if it is between 0 and 40V.

If an SSM is coded NCD: bit (30,31) = (1,0) on the output label, it indicates an input voltage of less than - 2V.
(8) High level AC (HLAC)


AC voltage measurements where the measurement range is between 0 and 160VRMS. Between 10 and 160V, the transmitted value is proportional to the voltage.

If an SSM is coded FW (failure warning): bit (30,31) = (0,0), it indicates the absence of input AC voltage and an offset voltage of less than -10V.

(9) Frequencies


The same input pin as high level AC is used. On the output label, the frequency is transmitted when it is between 300 and 500 Hz for a voltage between 80 and 200V. When the input voltage is less than 80V, the zero value is transmitted.

(10) Resistances


The parameters to be transmitted are temperatures. The measurement range is between 68.27 and 242.70 ohms.

If, on the output labels corresponding to these parameters, an SSM is coded NCD: bit (30,31) = (1,0), it indicates an open circuit at the input or a short circuit.

(11) Supplies and miscellaneous


Power supply for the SDAC and pins dedicated to maintenance.
B. Interface Tables


All the input/output are given in tabular form in the ECAM System Logic Data (ESLD) (SDAC Signals).

System Description

3. System Description

A. Functional Description

The SDAC performs:
- acquisition of the ARINC 429 data

- acquisition of the discrete data

- acquisition of the analog data

- concentration of these data and retransmission in the ARINC 429 format through the data buses. The discrete data are acquired and digitized in boolean data on ARINC word. Furthermore, some of these discretes are inverted to work in positive logic.
The analog signals are acquired and an encoding law is applied to the electrical value to give the physical measured value.

- monitoring of its internal functions

- generation of specific data (e.g. power supply and control).

4. Component Description

A. General Architecture

The general architecture of the SDAC is as follows:

(Ref. Fig. SDAC - Architecture of the Unit SHEET 1)
(Ref. Fig. SDAC - Architecture SHEET 1)
- five functional boards
. one CPU board
. one ARINC acquisition board
. two discrete/synchro acquisition boards
. one analog acquisition board

- three spare boards

- one OBRM

- one power supply module

- one backplane connector interface board

- one bus interface board.

The architecture is organized around the CPU board, which concentrates and manages the various types of acquisition received either directly or from the ARINC board, the two discrete/synchro boards or the analog board.
The CPU board communicates with the other boards through the Embedded Computer System Bus (ECSB).
The power supply module generates the +5 V, -15 V and +15 V voltages and the ECSB signals related to short cuts and undervoltages.
The backplane connector interface board ensures the connection between the back connector and the bus interface board. It contains the protection against the load short circuits, lightning and EMI.
The bus interface board ensures the connection between the back connector and the functional boards including the ECSB. It supplies the saved +5 V.
B. CPU Board

This board, to the ECSB standard, performs the functions below:
(1) It stores and executes the programs of the computer for which it acts as a CPU.
(2) Monitoring

This function is achieved by a circuit used for monitoring and memorizing data on the on board software (watchdog SMILE). It inhibits the outputs associated with the CPU fault and can communicate the source of this failure through one of the output buses.
(3) Memorization
(4) It manages the ECSB in its maximum configuration
(5) Connection with the ports

- control port
This port is used to drive the RESET signal for the inputs/outputs, perform the self tests on reset and transmit the system failures.

- status port
This port takes into account the internal data from the inputs/outputs and the power supply module.

(6) It manages the ARINC 429 outputs
(7) Acquisition of the discrete inputs

C. Discrete/Synchro Input Board

There are two identical discrete/synchro input boards.
Each board to the ECSB standard enables:
- the acquisition of discrete inputs and transformation into hybrid signals.

- the acquisition of synchro inputs.

The computed values of the synchro position (in degrees) are transmitted to the analog input board.
The functions of the synchro acquisition are:
- signal selection (consistency of data)

- formatting

- demodulation

- filtering

- analog to digital conversion (A/DC) on the analog input board.

These acquisitions are transmitted to the CPU via the ECSB.
D. Analog Input Board

The function of the board is to convert the analog data received on the inputs to digital format to be provided to the ECSB.
This board can acquire LLDC, HLDC, HLAC and Temperature data.
It also converts the synchro data from the discrete boards.
It multiplexes the input channels to one output channel.
E. ARINC Input Board

This board to the ECSB standard performs the following functions:
- it acquires ARINC 429 buses at high or low speed (12.5 or 100 kHz). Each bus contains normal labels or labels transferring data frames (maintenance data, P/N and S/N, etc...)

- it checks the validity of the received messages (parity, refresh, high or low speed, ...)

- it selects the labels required on each bus

- it stores the ARINC data and associated parameters (datation, parity, refresh, ...)

- it performs the self test

- it manages the labels transferring data frames by interruption of the ECSB

F. Power Supply Module

This module performs two functions:
- Power supply of the electronic boards which include integrated logic (+5 V) and analog circuits (+ and - 15 V) from the aircraft 115 V 400 Hz network.

- Generation of its own monitoring and control signals.

[Wodrick]

Now Spanners could you just explain all that for a 13 y o :)

[BOAC]

I thought he had:p More popcorn please................

These 13 yr olds can be quite clever, you know.

[Wodrick]

One's tongue was firmly in one's cheek :)

[BOAC]

Never mind the 13 yr old - what about the 64 yr old........?:)

[Wodrick]

As this 64 Y O (retired now) worked on the things for a long time he understood it perfectly.

[AF330]

Thanks spannersatcx,
Will study your reply and will come back if I have any doubts.

[spannersatcx]

The SDAC gets analogue and digital inputs and discretes from lots of systems from all over the a/c processes then and displays them through DMC's.

It gets 115vAC from the AC bus and processesd it through it's own onboard power supply boards.

But that would be too simple.

[Metro man]

Aren't the flight warning computers involved with ECAM ?

[spannersatcx]

Aren't the flight warning computers involved with ECAM ? yes, see Gryphon's first post.