/* * Copyright (c) 2001 Stephen Williams (steve@icarus.com) * * This source code is free software; you can redistribute it * and/or modify it in source code form under the terms of the GNU * General Public License as published by the Free Software * Foundation; either version 2 of the License, or (at your option) * any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ /* * This program demonstrates a tricky aspect of the Verilog syntax. * The problem is with the repeat statement. In fact, there is a * question as to whether it is a repeat statement at all, or an * event statement with a repeat modifier. These are the possibilities: * * procedural_timing_control_statement ::= * delay_or_event_control statement_or_null * * delay_or_event_control ::= * event_control * | repeat ( expression ) event_control * * If this interpretation is used, then ``repeat (5) @(posedge clk)'' * should be taken as a delay_or_event_control and the thread will * block until the 5th clk posedge. * * loop_statement ::= * repeat ( expression ) statement * * If *this* interpretation is used, then ``repeat (5)'' is the loop * head is used and the statement in the example is executed 5 times. * * These two interpretations both appear to be perfectly valid. However, * real tools use the loop_statement, so the standard must be considered * broken and this interpretation used. */ module main; reg clk = 1; always #5 clk = ~clk; initial #1 repeat (5) @(posedge clk) begin if ($time !== 10) begin $display("FAILED -- $time = %t", $time); $finish; end $display("PASSED"); $finish; end endmodule // main