Скачать или смотреть Solving the Issue of Cannot See RAM Contents in Simulation for SRAM Memory Design

Discover the troubleshooting steps to successfully access and visualize RAM contents in your SRAM memory design using Verilog simulation.
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This video is based on the question https://stackoverflow.com/q/65539895/ asked by the user 'pauk' ( https://stackoverflow.com/u/14674494/ ) and on the answer https://stackoverflow.com/a/65540901/ provided by the user 'toolic' ( https://stackoverflow.com/u/197758/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting SRAM Memory Design: Accessing RAM Contents in Simulation

Designing and simulating SRAM (Static Random Access Memory) can be a complex task, especially when you're trying to ensure that the contents of your memory are correctly accessed and visualized during simulation. One common issue many designers encounter is the inability to see anything when accessing RAM contents in simulation. In this guide, we'll explore a scenario where a user couldn't retrieve memory contents in their SRAM design and provide a clear solution to resolve it.

Understanding the Problem

The issue arises when the user attempts to simulate a circuit designed with SRAM characteristics. Let's outline the specifics of the situation:

The memory is clocked with a write enable signal, indicating when data can be written or read.

There is an address input to specify where the data goes or comes from.

In a user-defined module, write operations are facilitated without needing to specify an address directly.

However, the user experiences an unexpected result: even though values are supposed to be written to the memory, they find that they cannot retrieve any meaningful data during simulation.

The Code Overview

The user provided the following relevant portions of their Verilog code:

SRAM Module

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

User Interface Module

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

Test Bench

The test bench attempts to write different values into the SRAM:

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

Analyzing the Issue

Upon simulation, it was observed that:

The rd_data was consistently returning only the last value written to address 0, while reads from all other addresses returned X (unknown).

The code logic was set such that it only wrote values to the same memory address (address 0), due to the connection of the address_in signal always being 0.

Key Insight

Only writing to a single address leads to incomplete and incorrect data retrieval. To achieve the desired outcome, values need to be written to various addresses as specified in the design.

Solution Steps

To resolve this issue, the user needs to enable writing to different addresses rather than just the same address (0). Here’s how:

Modify the User Module: Connect the address signal to the address_in input of the sram_1port_instructions module.

Original Line:

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

Updated Line:

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

This change ensures that the memory writes are spread across different addresses as intended in the design.

Conclusion

By following these modifications, the user should be able to successfully visualize and retrieve different values from the memory during the simulation. Ensuring that you have the correct signal connections in your design is crucial for successful testing and simulation performance.

If you find yourself unable to see the content in your RAM during simulation, revisit your signal assignments and confirm that you're writing to the intended addresses.

Now you can proceed with your SRAM design and enjoy smooth data retrieval!