(2)
Close the access door 824 (Ref. TASK 52-41-00-410-002).
(3)
Remove the access platform(s).
1EFF : ALL 1 31-53-34Page 408 1 1 Feb 01/05 1 1 1CES 1 SDAC - ACQUISITION/INTERFACE - DESCRIPTION AND OPERATION
________________________________________________________
1.
General
_______ The purpose of this document is to define the interfaces between the various aircraft systems and the SDAC.
2.
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 or resolvers
-low level DC
-
high level DC
-
high level AC
-frequencies
-resistances
-
supplies and miscellaneous. Except for supplies and miscellaneous, all these signals are available on the 3 high speed output buses (at 100KHz frequency). Each analog or digital parameter has a corresponding output bus SDI- label group. Each discrete or boolean parameter has a corresponding SDI/bit-label group. Each label includes an SSM (sign/status matrix) or bit pair (30, 31) which defines the validity of the parameter (s) contained in the label. The 2 SDACs are identical, interchangeable and wired in the same way (except 2 discretes which serve to differentiate SDAC 1 and 2 on their output buses). Therefore, each parameter acquired on the same input is given at the same time for the two SDACs.
A.
Wired Discretes There are two types of wired discretes: -P-A ground on this input corresponds to logic 0 on the bit of the output label corresponding to this input. Absence of ground corresponds to logic
1.
-P+
An open circuit on this input correponds to logic 0 on the bit of the
output label corresponding to this parameter. A DC voltage (from 18.5 to
36V) on this input corresponds to logic 1.
For these wired P+ and P- discretes when one or other of the input ports,
grouping 8 of the 16 discretes assigned to one label, fails, the SSM of
this label is failure warning coded, ie : bits (30,31)=(1,1).
Some discretes are wired permanently, at least for specific aircraft.
This concerns the pin programming which can be read on the output of
label 007.
R 1EFF : 001-049, 051-099, 101-105, 151-156, 1 31-54-00Page 1 1201-203, 1Config-1 May 01/05 1 1 1CES 1 An NCD coded SSM on this label, bits (30,31)=(1,0) indicates a parity error on these parameters (the number of these pins wired to the ground must be odd).
B. Booleans on Bus Each boolean on a SDAC input bus is recopied as on the output bus. Its validity, represented by the output label SSM is the same as on the input. However, if a parity error is detected on the input of a label, the output label will have the last correct value received with its SSM. If the error persists, the following cycle will have the same value with a failure warning coded SSM, (bits 30,31)=(1,1).
C. Analog Signals These are parameters requiring an integer label on the output label. However, some of these parameters correspond to special options and are only recopied onto the output buses if one of the programming pin is validated (connected to the ground). The absence of these parameters on the output bus indicates incorrect parity of the programming pins.
D. Digital on Bus Each of these parameters acquired by a SDAC input bus occupies one label on the output bus. The value to be transmitted requires a certain number of bits on the label which varies from one parameter to another. Parameters in digital form are repeated on the output bus without undergoing transformation. On output, the parameter retains its validity (SMM). However, in the event of a parity error, the boolean transmission rule applies, since failure warning parameters are coded (bits 30,31)= (0,0).
E. Analog on Synchro or RVDT Angular information requiring 3 input pins plus one for the reference voltage. The transmitted measurement ranges are as follows: 0. to 360. or -35. to +35. An NCD coded SSM, bits (30,31)=(1,0), on the output labels corresponding to these parameters, indicates an open circuit on the input or the absence of the reference voltage.
F. Low Level DC 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. The bottom part (M2) of the measurement range is set between 0 and 1V and the top part (M1) between 5 and 9V. Outside the measurement range, the output label has an NCD coded SSM, bits (30,31)=(1,0).
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