how to get system time in verilog

[starone]

verilog system time

Hi all,

i want to generate a random number in verilog with the system time as the seed.
the normal $random() generates a random value by taking the $time (simulation time) as its seed.
so, how do i get the "system time" in verilog (or) how do i generate random value with system time as its seed.

Thanks,
jala

 

[laxdad8992]

I could not find an elegant way, but here's how I did it - a system call to write the current time into a file, then read the file to get the info into verilog. The system call to "date" only works on *NIX - if you are on windows, you'll have to change that. Anyway, here's the code:

integer FP;
integer fgetsResult;
integer sscanfResult;
integer NowInSeconds;
reg [8*10:1] str;

// call "date" and put out time in seconds since Jan 1, 1970 (when time began, no doubt)
// and put the results in a file called "now_in_seconds"
$system("date +%s > now_in_seconds");                                                   

// open the file for reading
FP = $fopen("now_in_seconds","r");

// get a string from the open file - "fgetsResult" should be a 1 - you can test 
// that for completeness if you'd like
fgetsResult = $fgets(str,FP);

// convert the string to an integer - "sscanfResult" should also be a 1, and
// you can test that, too, 
sscanfResult = $sscanf(str,"%d",NowInSeconds);

// close the file...
$fclose(FP);  // closes the file

// use the number as a seed...
process::self.srandom(NowInSeconds);

I have run this in "ncverilog" and confirmed it on both Solaris and Linux systems.