VIS: pseudo-inputs, primary-inputs and clock

From: Hess Hodge (hhodge@cray.com)
Date: Tue Mar 12 2002 - 15:37:48 MST

  • Next message: Fabio Somenzi: "Re: VIS: pseudo-inputs, primary-inputs and clock"

    Hello,

    First, here is some background: I'm using VIS-1.4, and I'm using synopsys
    and edif2blif to create a blif file from verilog.

    Here are a few VIS questions for you:

    1) Once I read in the design, I notice that there are a number of
    pseudo-inputs associated with my registers, their names end in $INIT. So,
    these pseudo-inputs are there to model nondeterminism on the initial-state
    of these registers, right? How can I set these registers to a known
    initial-state?

    2) I also have a number of primary-inputs in my design. When I check my
    design I want to place a constraint on the inputs. Say, for example, I
    want to constrain inputs A and B so that it is never the case that
    both are set, ie !(A=1 * B=1). Is there a way to constrain the inputs?

    3) My verilog design has a clock input called "Lclk". I translate
    the verilog to edif and then to blif. The resulting blif file has a
    number of .latch statements like the following:

    .latch i_reset reset_reg re Lclk 2

    (input = i_reset, output = reset_reg, and it is clocked on the rising edge
    of Lclk, with an initial value of "dont care")

    Then, when I read this blif file into VIS, I get the following warning:
    vis> read_blif -v csi_inbound_ctrl.blif
    Warning: Variable Lclk is not used in csi_inbound_ctrl.

    Has my Lclk been abstracted out of the design at this point? Do I need to
    edit my blif file to include a .clock statement?

    Thanks!
    Hess Hodge



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