1. Assertions in OpenVera Assertions check for the occurrence of sequences during simulation Sequence is an ordered (maybe timed) series of boolean events Assertion sequences are checked during simulation to find a match Assertions can specify sequences which should always occur or should never occur

2. Components of an Assertion Parameters: Arguments can make the assertion flexible/generalizable Ports: Variables/registers checked in the assertion Clock: Need a “clock” to know when to sample signal values Event Definition: An event is a timed sequence of expressions which are evaluated during simulation Event matching is checked at each clock Events may be hierarchical Binding: An assertion needs to be bound to a module instance within which the assertion is checked

3. Assertion Example unit 4step #(parameter integer s0 = 0) // Define parameters (logic en, logic clk, // Define ports logic [7:0] result); // Define a clock to synchronize attempts: clock posedge (clk) { // Define expressions: event t_0 : (result == s0); event t_1 : (result == 6); event t_2 : (result == 9); event t_3 : (result == 3); event t_normal_s: // Define a precondition to limit reporting: if (en) then (t_0 #1 t_1 #1 t_2 #1 t_3); }

4. Assertion Example Continued // Define an assertion: assert c_normal_s : check(t_normal_s, "Missed a step."); endunit /* Bind the unit to one or more instances in the design. */ // bind module cnt : // All instances of cnt or bind instances cnt_top.dut : // one instance. 4step start_4 // Name the unit instance. #(4) // Specify parameters. (!reset, m_clk, outp); // Specify ports.

5. Assertion Attempts Assertion matches are attempted every clock If a sequence starts to match then it is checked until it fails or completely matches

6. Sampling Variables e1 is (posedge req), e2 is (negedge ack) Variables are sampled at the clock edge Variable values (and value changes) are registered at clock edge

7. Matching a Sequence e1 is (posedge req), e2 is (negedge ack) e1 #3 e2 Sequence matching starts when e1 occurs Matching finishes 3 cycles after e1 No matching 1 or 2 cycles after e1

8. Matching a Sequence with a Variable e1 #3 (ack == 0) Can also match on variable level rather than edge

9. Multiple Sequences of Evaluation e1 #[1..3] (ack==0) e1 #1 (ack==0) e1 #2 (ack==0) e1 #3 (ack==0) Timing ranges causes matching to branch out to check multiple alternatives