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 GPWS - Outputs
 Figure 004

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 -
both discrete outputs are also used to inhibit automatic call out when the GPWS or G/S warnings are in progress.

 -
both discrete outputs are also used for the Digital Flight Data Recorder (DFDR).

 -------------------------------------------------------------------------------NAME ELECTRICAL LEVEL TO SIGNAL STATUS -------------------------------------------------------------------------------FAULT LEGEND GND/OC SYS P/BSW/SDACs GND = VALID G/S VISUAL ALERT GND/OCFWCsGND = VALID GPWS LEGEND GND/OCFWCsGND = VALID -------------------------------------------------------------------------------
F. Monitor Output The monitor output from the GPWC controls the FAULT legend of the SYS pushbutton switch .
 G. Bus Output The bus output could be used by the aircraft integrated data system (AIDS) (data management unit (DMU) and by the Centralized Fault-Display Interface - Unit (CFDIU) for test causes.
 H. Audio Output The audio output is used by the cockpit loud speakers for aural warning messages.
 4. Power Supply
____________ (Ref. Fig. 004) The GPWC power supply circuits receive 115VAC, 400 Hz, single phase (20 W max.) supply from the aircraft AC power and converts this supply to the following DC levels: plus or minus 15VDC from linear regulators with current limiting
 + 5VDC from a compensated switching regulator with current limiting
 -30VDC from a voltage doubler, fed by the 15VDC regulated supply.
 5. Component Description
_____________________
 A. GPWC (1WZ)
 (1) Description
 (Ref. Fig. 005)
 (a) The GPWC comprises an ARINC 600-2MCU case, housing interfacing, computing and warning output circuits.
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 GPWC Figure 005 
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 (b)
 The face of the GPWC contains a STATUS/HISTORY test switch and associated 8-character, alpha-numeric BITE display. If the STATUS/HISTORY switch is momentarily set to PRESENT STATUS, the BITE display provides a sequential readout of system operational status. If the STATUS/HISTORY switch is momentarily set to FLIGHT HISTORY, the BITE display provides a sequential readout of system faults stored from the previous 10 flights.

 (c)
 The back of the GPWC contains an ARINC 600, shell size connector to provide electrical connections to the aircraft wiring via mount. Contact grouping is as follows:

 -Top contact set - ATE interface + system interconnections
 -Center contact set - System interconnections
 -Bottom contact set - Power supply and bonding.
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 (2) Operation
 (Ref. Fig. 006)
 (a)
 Input/output circuits The input/output circuits contain six ARINC 429 receivers. Each receiver converts specified ARINC 429 format serial digital data to 32-bit parallel words for storage in a Random Access Memory (RAM). Data is accessed from RAM and checked for updating by the processor/voice/memory circuit. Discrete inputs to the GPWC are detected by ground sensing buffers and converted to a digital word. An ARINC 429 transmitter provides the GPWS output data words in ARINC 429 format (label 270 octal) for the Data Management Unit (DMU) and the maintenance labels for the CFDIU. Discrete outputs for the FAULT legend of the SYS pushbutton switch are provided by over-voltage and reverse-voltage protected lamp drivers.

 (b)
 Processor/voice/memory The processor/voice/memory consists of a 16-bit microprocessor (with associated timing and buffer circuits), program and voice memories, delta modulator, serial data stream generator, serial communication port, interrupt controllers and various associated logic. The 16-bit microprocessor is driven by a 4 MHz clock and is monitored by a watchdog timer. The watchdog timer resets the processor in the event of an incomplete program iteration. The aural warning messages reside in two 64 Kbytes X 8 Erasable Programmable Read Only Memories (EPROMs). The vocabulary for the messages can be defined by an alternate audio alert select discrete input. When a message is required for broadcast, the associated bits are converted from parallel to serial format and shifted into the delta modulator. The audio output is filtered, amplified and isolated to provide a suitable signal for the cockpit loud speakers. Data storage in the scratchpad memory is achieved using two 8 Kbytes RAMs. Fault history data is stored in an Electrically Erasable Programmable ROM (EEPROM) which is also used to store present flight characteristics data for use after momentary power losses. The program memory resides in 64 Kbytes EPROMs. The EPROMs are ultra-violet light erasable.
　
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