| Operator | Name | Description |
|---|---|---|
term [*N] |
Consecutive Repeat | Happens N times in a row. |
term [->N] |
Goto Repeat | Happens N times (gaps allowed), sequence ends EXACTLY on Nth occurrence. |
term [=N] |
Non-consecutive | Happens N times (gaps allowed), sequence can end anytime after. |
SVA Temporal Operators
The real power of SVA is in concisely describing timing constraints. This guide covers the essential Delay, Repetition, and Goto operators.
Operator Overview
Detailed Examples
Consecutive Repetition [*]
// "Start signal must be high for exactly 3 clocks"
start [*3]
// Equivalent to: start ##1 start ##1 startGoto Operator [->]
// "Wait for 'done' to go high. Gaps allowed."
// As soon as 'done' goes high, matched.
req |=> ##1 done[->1];
// Often used in handshakes:
req |-> ##1 ack[->1];Delay Ranges
Variable delays allow flexible checking.
// Grant must come within 1 to 5 cycles
req |-> ##[1:5] grant;
// Unbounded wait (Eventuality)
req |-> ##[1:$] done;
Warning: Use unbounded ranges (
$) carefully in simulation as
they can hurt performance if never satisfied.
Common Interview Questions
Q: Difference between [=1] and [->1]?
a[->1] (Goto) means the sequence ends *at the very cycle* 'a' occurs.
a[=1] (Non-consecutive) means the sequence matches *at or after* 'a' occurs
(non-greedy). Use [->1] if you want to trigger the next step immediately.