AFED-424A 24 Channel Discrete Input Module

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AFED-424A 24 Channel Discrete Input Module
Product Sheet
Product Sheet

The AFED-424A monitors the status (high/low) of up to 24 differential-ended discrete input channels.

Key Features

  • 24 differential ended, discrete, bi-level input channels
  • 24 independent, 32-bit counters with ten different operating modes
  • 40 ns internal resolution
  • FIFO based time tagging
  • High bandwidth (1 MHz)
  • Detection of 0.5 μs wide input signal pulses


  • Engine speed measurement
  • Data capture from a parallel bus
  • Timestamping of events
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AFED-424A 24 Channel Discrete Input Module

The AFED-424A monitors the status (high/low) of up to 24 differential-ended discrete input channels. Each of these has an assigned programmable 32-bit counter. Additionally, each of the inputs can be used to trigger time-tagged events.

Each counter can be programmed to operate in one of the following modes: Period, Pulse Width, Duty Cycle, Frequency, Events Since Sample, Events Since Power Up, Events Since Trigger, Samples Since Power Up, Samples Since Event, or Time Since Event. The range of each counter is programmable, as is the threshold (within ±28V), hysteresis (0.8 to 20V), and sensitivity to the rising/falling edge.

All the channels control the time tagging to the 1K word deep FIFO (96 bits wide each word). For each input, time tagging can be triggered by a rising edge, falling edge, both edges, or neither (when the channel is disabled). Every time a trigger occurs, a 96-bit word is written to the FIFO consisting of the 24 inputs (configurable to be either input state after the change or value representing the bits that triggered the event) and the 64-bit time at which the event happened. You can choose to store up to 60 bits IRIG time or 64-bit IEEE 1588-2004 Precision Time Protocol version 1 (PTPv1) time in the FIFO. There are also three FIFO flags that indicate that the FIFO is empty, that a message has been skipped, or that a message is stale.


Aerospace Instrumentation Brochure

Modern aerospace instrumentation systems can be highly complex, and it can be difficult to know how to meet program needs. It’s not unusual for requirements to change during a campaign and cause significant delays, and data must be captured reliably no matter what – otherwise expensive additional flights will be needed or months of program data could be lost. Read our brochure to learn how you can reduce your risk with commercial off-the-shelf (COTS) solutions. 

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