Specman e Event Scheduling

[Ritika Bishnoi]

How does Specman e event scheduling happens ?? I would like to understand the timings and execution, sequence and part of my code.

For SV we have these regions, and based on these we understand when and how what part of code works at what time... :

1. Preponed

Sampling in the preponed region is same as the sampling in the previous postponed region. All nets and variables used in concurrent assertions are sampled here.

The #1step sampling delay provides the ability to sample data immediately before entering the current time slot. #1step sampling is identical to taking the data samples in the Preponed region of the current time slot.

2. Active region

Sampling of blocking assignments (out = in), continuous assignments (assign out=in) and RHS of non-blocking assignments (out <= in) are evaluated in this region. If intra-assignment delay exist for blocking assignment, it first computes RHS value and then suspend the executing process and schedule as future event. Delay 0 will be scheduled for inactive region.

3. Inactive region

The Inactive region holds the events to be evaluated after all the Active events are processed.

#0 delay statements are executed in this region.
out = #0 in

An explicit #0 delay control requires the process to be suspended and an event to be scheduled into the Inactive region of the current time slot so that the process can be resumed in the next Inactive to Active iteration.

4. NBA

RHS of non-blocking assignment are occurred in active region and update of LHS will happen in NBA region.

The NBA region holds the events to be evaluated after all the Inactive events are processed. If events are being executed in the active region set, a non-blocking assignment creates an event in the NBA region scheduled for the current or a later simulation time.

5. Observed region

The Observed region is for evaluation of property expressions when it is triggered. During property evaluation, pass/fail code shall be scheduled in the Reactive region of the current time slot. PLI callbacks are not allowed in the Observed region.

6. Re-Active region

The pass/fail code (code in action blocks of concurrent assertions) is scheduled in this region. The code specified by blocking assignments in program blocks is also scheduled in this region.

The Reactive region is the reactive region set dual of the Active region.

7. Re-Inactive region

#0 delay statements related to program block are scheduled in this region.The Re-Inactive region holds the events to be evaluated after all the Reactive events are processed.

The Re-Inactive region is the reactive region set dual of the Inactive region.

8. Re-NBA region

The Re-NBA region holds the events to be evaluated after all the Re-Inactive events are processed.

Update of LHS will happen in this region for the statements its RHS of non-blocking assignment occurred in re-active region.The Re-NBA region is the reactive region set dual of the NBA region.

9. Postponed

Write values to any net or variable or scheduling an event in any previous region within the current time slot are illegal in this region. $monitor, $strobe, and other similar events are scheduled here.

[EDA Playground]

I'm sorry - I don't know much about e. I do know this, however: Regions 6,7 and 8 in System-Verilog mimic (I think) the fact that when you cosimulate e and an HDL, the simulators ping pong. ie The HDL simulator runs for 1 cycle, then the e simulator runs for 1 cycle and so on. The idea with System-Verilog was that your design used regions 2, 3 and 4 and your testbench used regions 6,7 and 8 (by using program blocks),

Have you tried asking this question on Stack Overflow?

Matthew