-an ARINC 429 transmitter.
The processor board uses the PTP and TTP signals sent by the
transducer board and the transducer modelling coefficients stored
in the NVM to compute the pressure.
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R Air Data Module
R Figure 006
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1 1
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Air Data Module
Figure 006A
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ADM - Block Diagram
Figure 007
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(c) EMI/lightning board
This board comprises the following devices:
-power supply: the ADM is supplied by the associated ADIRU with +/- 13.5VAC. Power consumption is less than 200 mA on the +13.5VDC input and less than 50 mA on the -13.5VDC input.
-EMI filters
-lightning protection
-input discretes filtering.
(2) Modes of operation The ADM has three modes of operation:
-initialization
-normal operation
-Memory Access/Calibration (MA/C).
(a)
Initialization mode The ADM automatically enters the initialization mode immediately after power is applied to the device or after a Watchdog Timer is activated due to an ADM failure. The ADM performs several tasks while in the initialization mode. It:
-initializes software variables and hardware interfaces
-performs various self-monitoring tests to determine if the ADM operates properly
-reads the fixed Program Pin discretes.
The ARINC 429 bus is disabled during the initialization mode. The
ADM does not output any data on the ARINC 429 bus.
The initialization mode is completed within 900 ms (maximum)
after valid power is applied to the ADM. Upon completion of the
initialization mode, the ADM automatically enters the normal
operation mode.
(b)
Normal operation mode The ADM enters the normal operation mode after the completion of the initialization mode. It remains in the normal operation mode until either power is removed from the ADM, or an internal failure activates the Watchdog Timer, or an internal BITE detects an unsafe condition at which time a failure warning is annunciated or ARINC 429 transmissions cease. The ADM performs the following functions in the normal operation mode. It:
-measures the pressure and temperature outputs from the transducer
-uses filtering or averaging techniques consistent with the noise, resolution, and dynamic frequency response requirements
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-computes the Applied Pressure based upon the pressure and temperature signals
-filters the Computed Pressure
-formats the ARINC 429 word to be transmitted
-transmits the ARINC 429 Computed Pressure word
-formats and transmits two ADM discrete words (labels 270, 271)
-reads and debounces the MA/C discretes
-performs the BITE functions
-formats and transmits ADM software and equipment I.D. words (labels 040,377).
(c) Memory Access/Calibration mode The Memory Access/Calibration (MA/C) mode is used for purposes of transducer calibration and fault analysis. The MA/C mode requires external test equipment which interfaces to the ADM via a RS-232C bus. This mode can be considered as an auxiliary mode which is accessible in a repair shop environment only.
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(3) Discrete inputs
Table 1 gives the identification of the ADM discrete inputs:
--------------------------------------------| ADM Pin | Identification | --------------------------------------------| K | SDI 1 (LSB) (2) | | L | SDI 2 (MSB) (2) | | M | Configuration code 1 (3) | | N | Configuration code 2 (3) | | P | Parity (1) | | a | Memory Access/Calibration 1 | | b | NVM reset discrete | | c | Memory Access/Calibration 2 | --------------------------------------------
Table 1 = Discrete Inputs
NOTE : (1) An odd number of pins K, L, M, N and P must be grounded to
____ signify a valid installation. After the desired Source Data Identifier (SDI) and the configuration pins have been selected, the parity pin P must be selectively left open or grounded to ensure that an odd number of pins K through P inclusive have been grounded.
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