Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

ASYNC_REG attribute for Altera FPGA

Hello everybody,

I'm doing a FLL design in VHDL. It works on Xilinx ISE by using the ASYNC_REG attribute on the proper signals.

Thus, I would like to know if something equivalent exists for Altera FPGAs (I am using Libero). Otherwise, does anyone know how I can fix this kind of problem ?

Thanks,

M. Bund

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    What is an ASYNC_REG when it's at home?

    What exactly are you planning on doing with a Libero? Is this the Libero SoC from Microsemi? you realise this isnt Altera?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    Well, sorry I meant Quartus.

    From the Xilinx Constraints guide : "The ASYNC_REG timing constraint improves the behavior of asynchronously clocked data for simulation. Specifically, it disables 'X' propagation during timing simulation. In the event of a timing violation, the previous value is retained on the output instead of going unknown."

    I am looking for the same thing.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    Ok. I see what you mean

    The equivolent would be set_false_path <regA> <regB>, but you'll need to read up on SDC format on how to search for the registers.