VHDL-AMS problem

Discussion in 'VHDL' started by Tao Chen, Jun 14, 2005.

  1. Tao Chen

    Tao Chen Guest


    I am trying to define an a2d/d2a boundry myself. But "vacom" always
    give error on my codes:
    Error: The characteristic number (3) does not match the number of
    scalar equations (2) [LRM section 12.6.6]

    The VHDL-AMS codes are attached below. The purpose of the code is to
    convert two digital input "oscon_d" and "icon_d" into analog output
    "oscon_a" and "icon_a", and to convert the analog input "vout_a" into
    the digital output "vout_d".

    The reason seems to be that the equation number is smaller than the
    variable number. But one of my terminal ("vout_a") is connected to a
    spice netlist and its voltage is determined by the result of the spice
    simulation, so I cannot give the equation on that voltage. My question
    is, how should I deal with such a situation? Thanks!

    ------ The source file ---------
    library disciplines;
    use disciplines.electromagnetic_system.all;

    library ieee;
    use ieee.std_logic_1164.all;

    entity boundry is

    generic (
    tf : real := 0.1e-9; -- falling time
    tr : real := 0.1e-9; -- rising time
    vhigh : real := 1.8;
    vlow : real := 0.0;
    threshold:real := 0.9);

    port (
    signal oscon_d : in std_logic; -- oscon from digital to analog
    signal icon_d : in std_logic;
    signal vout_d : out std_logic;
    terminal oscon_a : Electrical;
    terminal icon_a : Electrical;
    terminal vout_a : Electrical);

    end entity boundry;

    architecture behavior of boundry is
    terminal ground : Electrical; -- global ground
    QUANTITY voscon ACROSS ioscon THROUGH oscon_a to ground;
    QUANTITY vicon ACROSS iicon THROUGH icon_a to ground;
    quantity vvout across ivout through vout_a to ground;
    signal oscon_eff : real;
    signal icon_eff : real;
    begin -- architecture behavior

    oscon_eff <= vhigh when (oscon_d = '1') else vlow;
    icon_eff <= vhigh when (icon_d = '1') else vlow;

    voscon == oscon_eff'Ramp(tr,tf);
    vicon == icon_eff'Ramp(tr,tf);

    vout_d <= '1' when vvout'above(threshold) else '0';

    end architecture behavior;
    Tao Chen, Jun 14, 2005
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