A property is an if...else kind if it has either the form

if (expression_or_dist) property_expr1

or of the form

if (expression_or_dist) property_expr1
 else property_expr2

A property of the first form evaluates to true if, and only if, either expression_or_dist evaluates to false or property_expr1 evaluates to true. A property of the second form evaluates to true if, and only if, either expression_or_dist evaluates to true and property_expr1 evaluates to true or expression_or_dist evaluates to false and property_expr2 evaluates to true. Below example shows the usage of the same.

Real usage example would be, check if command is read, if yes then check property read_property else check property write_property.

  1 //+++++++++++++++++++++++++++++++++++++++++++++++++
  2 //   DUT With assertions
  3 //+++++++++++++++++++++++++++++++++++++++++++++++++
  4 module ifelse_assertion();
  5 
  6 logic req,gnt,clk,check;
  7 //=================================================
  8 //  Clock generator
  9 //=================================================
 10 initial begin
 11  clk = 0; 
 12  forever  #1  clk ++;
 13 end
 14 //=================================================
 15 // Simple DUT behaviour
 16 //=================================================
 17 logic gnt2;
 18 initial begin
 19   gnt2 <= 0; gnt <= 0;
 20 end
 21 always @ (posedge clk)
 22 begin
 23   gnt2 <= req;
 24   gnt  <= gnt2;
 25 end
 26 //=================================================
 27 // Test Vector generation
 28 //=================================================
 29 initial begin
 30   req <= 0;check <= 0;
 31    #3  req <= 1;
 32    #10  req <= 0;check <= 1;
 33    #3  req <= 1;
 34    #5  req <= 0;
 35    #1  $finish;
 36 end
 37 //=================================================
 38 // A ifelse property
 39 //=================================================
 40 property delay1;
 41     req  ##1  gnt;
 42 endproperty
 43 property delay2;
 44     req  ##2  gnt;
 45 endproperty
 46 // See the OR operator
 47 property ifelse_prop;
 48   @ (posedge clk)
 49     if (check)
 50        delay1
 51     else
 52        delay2;
 53 endproperty
 54 //=================================================
 55 // Assertion Directive Layer
 56 //=================================================
 57 ifelse_assert : assert property (ifelse_prop);
 58 
 59 endmodule

 "ifelse_assertion.sv", 57: ifelse_assertion.ifelse_assert: 
 started at 1s failed at 1s
         Offending 'req'
 "ifelse_assertion.sv", 57: ifelse_assertion.ifelse_assert: 
 started at 3s failed at 3s
         Offending 'req'
 "ifelse_assertion.sv", 57: ifelse_assertion.ifelse_assert: 
 started at 15s failed at 15s
         Offending 'req'
 "ifelse_assertion.sv", 57: ifelse_assertion.ifelse_assert:
  started at 17s failed at 19s
         Offending 'gnt'
 $finish called from file "ifelse_assertion.sv", line 35.
 

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Deepak Kumar Tala - All rights reserved

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