Unleashing the Power of Automatic Functional Netlist ECO: Achieving What Manual ECO Alone Cannot

When faced with a bug requiring functional netlist ECO, designers often struggle with the decision of whether to opt for manual or automatic methods. While manual ECO may appear to offer more flexibility in handling small patches, it is important to note that automatic ECO using a comprehensive tool can often achieve what manual ECO cannot. Moreover, the time and effort saved by leveraging automatic ECO are significant.

Consider the scenario of modifying a large state machine as an example of functional ECO. In this case, a specific state transition requires the addition of another condition involving a substantial combinational signal. The RTL change introduces a new combinational signal called 'new_large_comb' into the state transition condition.

case(current_state)
...
STATE17: if(one_existing_comb & new_large_comb) next_state = STATE19;
...        

Generating the new Reference netlist through synthesis results in the optimization of all related combinational signal names. Consequently, it becomes challenging to perform reverse engineering and identify the location of the ECO by solely inspecting the schematic. The potential area where the modification may have occurred is illustrated in the following figure:

While it is possible to eventually determine the ECO location by manually inspecting the schematic, this approach is time-consuming and requires significant effort. However, by employing GOF ECO, the ECO location can be easily identified in the Implementation netlist, as shown below:

By employing its comprehensive algorithm, GOF ECO identifies four new gates that effectively rectify the logic, ensuring that the ECOed design becomes equivalent to the newly synthesized Reference netlist. The algorithm is designed to minimize disturbances to the existing logic, resulting in minimal timing impact and reducing the need for extensive design iterations.

In summary, automatic ECO offers significant advantages by saving considerable time and effort in the design process. This efficiency leads to a faster turnaround time, allowing for quicker time to market for the product or project at hand.

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