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Getting Unix time or epoch in VHDL

To introduce some randomness in my testbench I would like to use pseudo-random numbers seeded with the current Unix time or epoch. Is there a (non-synthesizable ofc) function in VHDL for that? I need it to work in VHDL 2008.

Solution

  • Why not simply passing a generic parameter value on the same command line you use to run the simulation? Example with bash:

    entity foo is
  generic(seed: natural := 0);
end entity foo;

architecture bar of foo is
begin
  assert false report natural'image(seed);
end architecture bar;

    $ ghdl -a --std=08 foo.vhd
$ ghdl -r --std=08 foo
foo.vhd:7:3:@0ms:(assertion error): 0
$ ghdl -r --std=08 foo -gseed=$(date +%s)
foo.vhd:7:3:@0ms:(assertion error): 1648027085