Hi, All - A clarification question came up in one of my SystemVerilog classes regarding the $past number_of_ticks argument. A student questioned whether the argument could be an expression and I believe the answer is no, but LRM does not definitively make a precise definition. There is no BNF to describe the $past arguments. I did a SVDB search on number_of_ticks and only found Mantis item 1591, which did not cover the topic. Proposal (if my assumption is correct): 17.7.3 Sampled value functions Bottom of page 247 WAS: number_of_ticks must be 1 or greater. If number_of_ticks is not specified, then it defaults to 1. $past returns the sampled value of the expression that was present number_of_ticks prior to the time of evaluation of $past. A clock tick is based on clocking_event. If the specified clock tick in the past is before the start of simulation, the returned value from the $past function is a value of X. PROPOSED: number_of_ticks must be an integer constant of 1 or greater. If number_of_ticks is not specified, then it defaults to 1. $past returns the sampled value of the expression that was present number_of_ticks prior to the time of evaluation of $past. A clock tick is based on clocking_event. If the specified clock tick in the past is before the start of simulation, the returned value from the $past function is a value of X. Regards - Cliff ---------------------------------------------------- Cliff Cummings - Sunburst Design, Inc. 14314 SW Allen Blvd., PMB 501, Beaverton, OR 97005 Phone: 503-641-8446 / FAX: 503-641-8486 cliffc@sunburst-design.com / www.sunburst-design.com Expert Verilog, SystemVerilog, Synthesis and Verification Training -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.
This archive was generated by hypermail 2.1.8 : Thu Mar 08 2007 - 23:34:44 PST