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-to: team@leaflabs.com
-subj: paper review: "Nonblocking Assignments in Verilog Synthesis..."
-
-TL;DR: this is something like a "goto considered harmful" w/r/t using confusing
-blocking assignment in (non-sythesizable?) Verilog.
-
-# Context
-
-This paper was written in 2000 and seems to target Verilog programmers who
-write non-synthesizable simulation code. Despite the word "Synthesis" in the
-title. After reading, the implication that this paper might have any new
-insights for an engineer whose failure might "kill" stikes fear in my gut.
-
-Apparently this won a "Best Paper" award at a conference back when it was
-published.
-
-On page 15 there is a note about about synthesis performance: "The latter would
-be inefficient from a simulation time perspective"; perhaps this was the
-historical temptation of these bad practices?
-
-# Judgement
-
-There's really nothing new here (for jess/aj/bryan at least): for sequential
-logic use nonblocking assignment in always@ blocks, and for combinatoral logic
-use 'assign' statements outside of a block, unless you have something really
-tight and complicated going on, in which case use an always block with a
-carefully selected sensitivity list and all blocking assignments inside.
-
-# Nuggets
-
-From page 20: "Nonblocking assignments are updated after all $display
-commands". I did not know this! The example given is pretty good; $strobe is
-recommended as the alternative:
-
-    module display_cmds;
-        reg a;
-        initial $monitor("\$monitor: a = %b", a);
-        initial begin
-            $strobe ("\$strobe : a = %b", a);
-            a = 0;
-            a <= 1;
-            $display ("\$display: a = %b", a);
-            #1 $finish;
-        end
-    endmodule
-
-gives:
-
-    $display: a = 0
-    $monitor: a = 1
-    $strobe : a = 1
-
-# Appendix: Verilog Coding Guidelines
-
-Verbatim from paper:
-
-1: When modeling sequential logic, use nonblocking assignments.
-2: When modeling latches, use nonblocking assignments.
-3: When modeling combinational logic with an always block, use blocking
-.
-4: When modeling both sequential and combinational logic within the same always
-nonblocking assignments.
-5: Do not mix blocking and nonblocking assignments in the same always block.
-6: Do not make assignments to the same variable from more than one always block.
-7: Use $strobe to display values that have been assigned using nonblocking
-.
-8: Do not make assignments using #0 delays.