How to Create a Falling Edge Detector
Overview
Edge detection is a key technique for identifying signal changes from high to low, known as a falling edge, to trigger specific actions. It ensures precise timing and accurate responses in applications like event triggering, timing analysis, and signal synchronization. By reliably detecting these transitions, edge detection enables systems to respond promptly and maintain high precision.
The Configurable Logic Block (CLB) has built-in edge detectors that automatically synchronize input signals with the CLB clock. When an external signal enters unsynchronized, the edge detectors align it with the internal clock, ensuring stable transitions and reducing timing issues.
Figure 1: Falling Edge Detector Circuit
Requirements
Procedure
Implement the CLB Logic
Configure the CLB to implement flip-flops, AND gates, or equivalent logic for the falling edge detector. Refer to Figure 1 for guidance.
Select a Clock Source for the CLB
Set the CLB to use the LFINTOSC clock source.
Assign Pins
Connect the input of the logic to the signal where you want to detect a falling edge, and route the output, which represents the detected falling edge, to the desired destination in your system.
Verify the Design
Confirm the falling edge functionality using a debugging tool to ensure proper operation.
Results
Figure 2 shows the output of the falling edge detection circuit. This circuit uses a combination of flip-flops, AND gates, and inverters to store the input signal's state and generate a pulse at the transition, detecting falling edges of the input signal. The falling edge detection output (D1) correctly responds to the transitions in the input signal (D0), providing clear, distinct pulses for each detected falling edge.
Figure 2: Falling Edge Detector Output