| // Icarus 0.7, cvs files from Feb 2, 2003 |
| // -------------------------------------- |
| // |
| // iverilog precision.v |
| // or |
| // iverilog -D DUMP precision.v |
| // vvp a.out |
| // |
| // Use & display of real time periods with `timescale set to 1 ns / 10 ps |
| // |
| // $simtime keeps time in 10ps increments |
| // $simtime cannot be displayed (yet) |
| // $simtime can be used in comparisons -- compared to times in 10 ps units |
| // $time should be $simtime-rounded-to-ns |
| // $time displays according to `timescale and $timeformat |
| // $time can be used in comparisons -- compared to times in 1 ns units |
| // |
| // Assuming that the simulation runs on units of 10ps, a clock which is set to |
| // change value every (15.2 ns)/2 should change every 7.6 ns, i.e. 760*10ps. |
| // |
| // The dumpfile shows a timescale of 10ps; therefore, it should show the clock |
| // changing every 760*10ps. It doesn't. The clock is changing every 700*10ps. |
| // The checks on the clock using $simtime below verify that the dumpfile is |
| // seeing what the simulation is, in fact, doing. |
| // |
| |
| `timescale 1 ns / 10 ps |
| |
| `define PERIODI 15 |
| `define PERIODR 15.2 |
| |
| module top; |
| |
| reg tick,clk, fail; |
| reg [31:0] ii; |
| |
| `ifdef DUMP |
| initial begin |
| $dumpvars; |
| end |
| `endif |
| |
| initial begin |
| $timeformat(-9, 2, "ns", 20); |
| |
| $display("integer & real periods: 'd%0d 'd%0d",`PERIODI,`PERIODR); |
| $display("integer & real periods (15.00, 15.20): 't%0t 't%0t",`PERIODI,`PERIODR); |
| $display("......... `PERIODR should be displayed as 15.20 in its timeformat."); |
| $display("integer & real periods: 'b%0b 'b%0b",`PERIODI,`PERIODR); |
| $display("integer & real periods: 'h%0h 'h%0h",`PERIODI,`PERIODR); |
| |
| clk = 0; |
| tick = 0; |
| fail = 0; |
| #1; |
| if($time === 1) $display("\t$time is in ns"); |
| if($time === 100) $display("\t$time is in 10 ps"); |
| $display("\ttime (1, 1h): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); |
| if($simtime === 1) $display("\t$simtime is in ns"); |
| if($simtime === 100) $display("\t$simtime is in 10 ps"); |
| $display("\tsimtime (100, 64h): 'd%0d, 't%0t, 'h%0h",$simtime,$simtime,$simtime); |
| #(`PERIODI - 1); |
| tick = 1; |
| if($time !== 15) begin fail = 1;$display("time (15, Fh): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 1500) begin fail=1; $display("simtime not 1500"); end |
| #(`PERIODR); |
| tick = 0; |
| if($time !== 30) begin fail = 1; $display("time (30, 1Eh): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 3020) begin fail=1; $display("simtime not 3020"); end |
| #(`PERIODR); |
| tick = 1; |
| if($time !== 45) begin fail = 1; $display("time (45, 2Dh): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 4540) begin fail=1; $display("simtime not 4540"); end |
| #(`PERIODR); |
| tick = 0; |
| if($time !== 61) begin fail = 1; $display("time (61, 3Dh): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 6060) begin fail=1; $display("simtime not 6060"); end |
| #(`PERIODR); |
| tick = 1; |
| if($time !== 76) begin fail = 1; $display("time (76, 4Ch): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 7580) begin fail=1; $display("simtime not 7580"); end |
| #(`PERIODR); |
| tick = 1; |
| if($time !== 91) begin fail = 1; $display("time (91, 5Bh): 'd%0d, 't%0t, 'h%0h",$time,$time,$time); end |
| if($simtime !== 9100) begin fail=1; $display("simtime not 9100"); end |
| |
| $display("\t\t**********************************************"); |
| if(fail) $display("\t\t****** time precision test FAILED *******"); |
| else $display("\t\t****** time precision test PASSED *******"); |
| $display("\t\t**********************************************\n"); |
| |
| $finish; |
| end |
| |
| initial begin |
| for(ii = 0; ii < 1524; ii = ii + 1) begin |
| #(0.01); |
| if(($simtime == 659) && (clk !== 0)) begin fail=1; $display("time: 659, clk wrong"); end |
| if(($simtime == 701) && (clk !== 0)) begin fail=1; $display("time: 701, clk wrong"); end |
| if(($simtime == 759) && (clk !== 0)) begin fail=1; $display("time: 759, clk wrong"); end |
| if(($simtime == 761) && (clk !== 1)) begin fail=1; $display("time: 761, clk wrong"); end |
| if(($simtime == 1399) && (clk !== 1)) begin fail=1; $display("time: 1399, clk wrong"); end |
| if(($simtime == 1401) && (clk !== 1)) begin fail=1; $display("time: 1401, clk wrong"); end |
| if(($simtime == 1519) && (clk !== 1)) begin fail=1; $display("time: 1519, clk wrong"); end |
| if(($simtime == 1521) && (clk !== 0)) begin fail=1; $display("time: 1521, clk wrong"); end |
| end |
| end |
| |
| always begin |
| #(`PERIODR/2) clk <= ~clk; |
| // clock should change as follows: |
| // T (10ps) : clk |
| // 0 : 0 |
| // 760 : 1 |
| // 1520 : 0 |
| // 2280 : 1 |
| // 3040 : 0 |
| // etc. |
| end |
| |
| endmodule |
