Constrained Random Value in verilog

[whizkid]

HI friends,
I want to assign a random value either +5 or -5 to a port . How do i
do that?
I tried $random function but it allows to assgin values between -5 and
+5 or 0 to 5 . But what i want is exactly +5 or else -5. Anyone know
how to do it ..

thanks
whizkid

 

[Gabor Szakacs]

If you only need two output values you really want a single
bit random function which returns 0 or 1.
Then use that bit to select -5 or +5 something like:
reg rval;
integer seed;
integer port;

forever begin
seed = 1;
rval = $random (seed);
port = rval ? +5 : -5;
. . .
end

whizkid@gamebox.net (whizkid) wrote in message news:<edfc084c.0410180647.4b8159a1@posting.google.com>...

HI friends,
I want to assign a random value either +5 or -5 to a port . How do i
do that?
I tried $random function but it allows to assgin values between -5 and
+5 or 0 to 5 . But what i want is exactly +5 or else -5. Anyone know
how to do it ..

thanks
whizkid

 

[Swapnajit Mittra]

whizkid@gamebox.net (whizkid) wrote in message news:<edfc084c.0410180647.4b8159a1@posting.google.com>...

HI friends,
I want to assign a random value either +5 or -5 to a port . How do i
do that?
I tried $random function but it allows to assgin values between -5 and
+5 or 0 to 5 . But what i want is exactly +5 or else -5. Anyone know
how to do it ..

thanks
whizkid

my_int = ($random%2*10)-5;

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[Steven Sharp]

gabor@alacron.com (Gabor Szakacs) wrote in message news:<8a436ba2.0410181001.2f80854a@posting.google.com>...

If you only need two output values you really want a single
bit random function which returns 0 or 1.
Then use that bit to select -5 or +5 something like:
reg rval;
integer seed;
integer port;

forever begin
seed = 1;
rval = $random (seed);
port = rval ? +5 : -5;
. . .
end

The approach to selecting between two values is good. However,
if you keep resetting seed to 1 every time before you call $random,
you will get the same (nonrandom) result every time too.