Can you explain the process of establishing an SVA in System Verilog to forbid memory operations throughout a power-on-reset?

Question Analysis

The question is asking about the process of using SystemVerilog Assertions (SVA) to ensure that memory operations are not allowed during a power-on-reset (POR) condition. This involves understanding both the concept of power-on-reset and how SystemVerilog Assertions can be used to monitor and enforce specific behavior in a hardware design. The candidate needs to know how to write assertions that trigger during the POR phase to prevent unintended memory operations.

Answer

To establish an SVA in SystemVerilog that forbids memory operations throughout a power-on-reset, follow these steps:

1. Understand Power-On-Reset (POR):

   • Power-on-reset is a condition where the system initializes its state upon powering up. During this phase, certain operations, like memory accesses, may need to be restricted to ensure a consistent and error-free startup.

2. Identify the Signals:

   • Determine which signals indicate the power-on-reset condition (e.g., reset_n) and which are related to memory operations (e.g., mem_read, mem_write).

3. Write the SVA:

   • Create assertions that monitor the reset_n signal and forbid memory operations during this period. Use the assert statement to define the condition that must hold true.

4. Implement the Assertion:

   • Here’s an example assertion in SystemVerilog:

   property no_memory_operations_during_reset;
      @(posedge clk)
      reset_n == 0 |-> !(mem_read || mem_write);
   endproperty
   
   assert property (no_memory_operations_during_reset)
      else $error("Memory operation occurred during power-on-reset.");
   

   • Explanation:
     • @(posedge clk): The assertion is sampled on the rising edge of the clock.
     • reset_n == 0 |->: This specifies that when reset_n is low (indicating a reset), the following expression must hold true.
     • !(mem_read || mem_write): Ensures that neither mem_read nor mem_write is asserted during the reset.
     • $error: If the condition is violated, an error message is generated.

5. Test the Assertion:

   • Simulate the design to ensure that the assertion triggers if a memory operation is attempted during the power-on-reset period.

By following these steps, you can effectively use SystemVerilog Assertions to prevent memory operations during a power-on-reset, ensuring the hardware design behaves correctly during initialization.