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SIMULATED Multifunction Keypad

Hardware Connectors

  1. Device Power

    The MKP is entirely powered by the 28VDC power input. There is no separate backlighting power input. All backlighting circuitry is powered by the 28VDC input and backlight dimming is controlled by commands on the ARINC interface. During power-up, a large current (over 600mA) is drawn to fill up a bulk capacitor. This inrush current will diminish shortly after power-up. However, it is recommended that the power supply driving the MKP can deliver a minimum of 1A.

  2. PWM Output

    The Simulated Multifunction Keypad is designed to power three additional light plates exterior to the unit. The circuitry is designed to deliver up to 200mA on each of the power outputs. These circuits are protected with a Positive Temperature Coefficient (PTC) self-resetting fuse. The circuitry is designed to hold up to 200mA and will trip at a maximum of 400mA. If the output is shorted, the output will stop delivering power until the fault has been resolved, without damaging the MKP. The corresponding return circuit (RTN) is pulse width modulated (PWM). The modulation period is commanded over the ARINC interface.

  3. ENTER OUT

    When the ENTER key is pressed, this signal is driven low. Even if the ENTER key is pressed for only a short moment, this output will be driven low for a minimum of 200ms. This signal is assumed to be pulled to a higher voltage across a resistor externally to the MKP. To protect the circuitry the circuit is protected by a PTC self-resetting fuse designed to hold up to 200mA and will trip at a maximum of 400mA.

  4. ARINC 429

    The Simulated Multifunction Keypad has one ARINC 429 input and one ARINC 429 output. Each differential pair follows the ARINC 429 standard.

  5. Demo Mode / Benchtop Testing

    During regular start-up, the Simulated Multifunction Keypad will have no backlight and no annunciator output, until a proper ARINC Label has been received. However, the MKP can be placed in “Demo Mode”. In this mode, the backlight can be controlled by the encoder, and the annunciator can be cycled through OFF-LOW-HIGH by pressing the “ENTER” key. Press and hold “SYS” + “CDU” + “INFO” for about 5 seconds. After 5 seconds the “LOWER MFD” label will blink blue several times. Wait until the light stops blinking and release the keys. The unit is now not responding to ARINC Labels. To return to normal operation, power will need to be cycled.

    This mode can also be used in bench top testing. If the unit is powered with regular 28VDC, enter Demo Mode as described above. However, if the unit is powered by a USB-C power supply, the MKP will enter Demo Mode automatically. If powered with a USB-C power supply, it must be able to deliver 20VDC and at least 3 Amps (60W and above).

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