Скачать или смотреть Designing a Verilog Counter with Button Input Handling

Learn how to create a `Verilog` counter that responds only to button presses, ensuring it counts correctly without constant increments.
---
This video is based on the question https://stackoverflow.com/q/64094723/ asked by the user 'K C' ( https://stackoverflow.com/u/14351898/ ) and on the answer https://stackoverflow.com/a/64094806/ provided by the user 'Light' ( https://stackoverflow.com/u/5461798/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Designing counter on Verilog with input button

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Designing a Verilog Counter with Input Button

When working with hardware description languages such as Verilog, designing a counter that accurately responds to input buttons can sometimes present challenges. Specifically, one common issue arises when implementing a counter that increments or decrements based on button presses. Many developers encounter the problem of a counter continuously incrementing as long as the button remains pressed. In this guide, we will explore a straightforward solution to this issue by ensuring that the counter only reacts to a change in button state.

The Original Problem

The initial query involves a binary counter designed to count based on three specific button inputs, which corresponds to values as follows:

001 counts + 1

010 counts -1

100 counts + 3

The original implementation in Verilog uses a push signal to read these inputs, which are connected to physical buttons. However, the problem arises when the button is held down; the counter continues to count upward indefinitely as the condition for counting remains met.

Breaking Down the Solution

Understanding the Button Behavior

The crux of the issue lies in how the button press is interpreted by the Verilog code. When a button is pressed, the push signal remains in the same state, thereby meeting the counting condition repeatedly. To effectively manage this, we need a mechanism to detect changes in the push input.

Introducing a Change Detection Mechanism

To solve this, we can implement a change detection routine within the counter module. This routine will monitor whether the push signal has changed from its last known state. Here’s how to set this up in Verilog:

Create a Register for the Previous State:
We declare a register that will store the last state of the push input and compare it with the current state during each clock cycle.

[[See Video to Reveal this Text or Code Snippet]]

Detect Changes on the Rising Edge:
By sampling the state of push at each clock cycle and assigning it to push_d, we can then compare the two states.

[[See Video to Reveal this Text or Code Snippet]]

Generate a Change Signal:
A push_chg wire will indicate if the push has changed from the last cycle.

[[See Video to Reveal this Text or Code Snippet]]

Evaluate Counts on Change:
Finally, modify the counting logic to only execute when push_chg is true, thus preventing the counter from incrementing while a button is held down.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By incorporating change detection for button presses in your Verilog counter, you can ensure that counting actions are only triggered by new button events rather than repeated conditions. This enhances the functionality and efficiency of your design, particularly in an FPGA setup.

With these adjustments, you can confidently implement a robust counter that responds accurately to push button inputs without the risk of unintended continuous counting.

If you’re working on a Verilog project and need more insights or solutions, feel free to leave a comment below!