Technical Handbook

Table Of Contents
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polled one by one. The event detect unit also has a built in integrity check. This function
works when the ILS is in normal operational mode (automatic mode with transmitters on and
no alarm). When the ON/OFF is pressed, a FORCE_AL signal is output. This signal turns off
all transmitters (PA 1234A) without notifying the rest of the system. The loss of transmitted
signal will be detected by the monitors (MO 1212) and cause monitor alarms to the STATION
CONTROL.This alarm will result in a TX changeover initiated by STATION CONTROL, but
since STBY TX is also turned off, monitor alarm will remain and cause TX shutdown after
alarm delay. This sequence ensures that the monitoring circuits and shutdown mechanisms
operates as intended. If the integrity check function should fail, a timeout function shuts the
ILS down.
INTERRUPT DETECT
This block detects transmitter state changes and stores the event causing the change. Trans-
mitter feedback and coax relay position is also stored. An interrupt is generated to inform the
RMS that a transmitter state change has occurred.
TX 20 SEC DELAY
This function ensures that no transmitters are allowed to transmit for 20 seconds after an
alarm shutdownhas occured.
MAIN SELECT STORE
This block stores the information regarding which transmitter that is selected as main transmit-
ter.
INTERLOCK DELAY
This block turns on the transmitters 20 seconds after the interlock signal from the REMOTE
CONTROL IF block has been deactivated.
9.1.3.3 NMP106A Station Control State Machine Control
General Description:
NMP106A is a FPGA within the STATION CONTROL block. It serves mainly as a state
machine controller (states are stored in an EPROM) for transmitter on/off control. NMP106A is
based on the Actel ACT1020 FPGA. For electrical specifications see the ACT1020 datasheet.
Block Diagram:
See Figure. 9-3
Block Description:
SEQUENCER
This block generates strobes and control signals for running the state machine. New states
are triggered based on received new data from NMP105A (on the STO_BUS). This block also
generates reset to the hardware watchdog safeguarding and controlling the station control
reset.
EVENT CHECK
This block checks event and main select signal received from NMP105A. Two identical event/
main select signals must be received in sequence before the event/main select is acted upon.
TIMER