cz172638 / darter Goto Github PK

Darter is very much a work in progress. The basic workflow is:

  * Build ibis_*.inc files (make).
  * Obtain a .ibs file from your vendor (eg, u69a.ibs).
  * Build the associated .lib file (darter.py u69a.ibs u69a.lib).
  * Create a schematic using the proper IBIS components:
      - Check in your .ibs file to see what [Model]'s are available.
      - Create a 'SPICE directive' with a .lib line for that [Model] (.lib
        u69a.lib DQ_FULL_533).
      - Select the gEDA IBIS symbol associated with the Model_type.
      - Fill in the in the symbol attribute (DQ_FULL_533).
          + Optionally add spec=-1/0/1 for slow, typ, and fast respectively
          + Optionally add start_on=1/0 to change the initial state of the
            buffer. With the default (start_on=1), the buffer starts in whatever
            state is indicated by its input. With start_on=0, the buffer will
            start tristated and then immediately transition to the state given
            by the inputs. The latter can help with convergence is some cases.
      - Connect up a digital stimulus to the IN and DRV pins if applicable.
      - Connect up the power and ground rails.
      - Connect together various models as in your own design.
      - Create a SPICE netlist from your schematic (gnetlist -g spice-sdb -o
        example.net example.sch).
      - Load the netlist in ngspice (ngspice example.net).
      - Run as appropriate (tran 1p 60n).
      - Plot the output (aka, go nuts).

Darter also supports pseudo-differential models. Add the suffix '_DIFF' for the
differential model. Threshold information is pulled from the '[Diff Pin]'
section or the '[Receiver Thresholds]'.

Pin parasitics are supported with additional subckts:

  * Add a .lib line for the component (.lib MT47H512M4EB).
  * Add the 'ibis_ebd-1.sym' component.
  * Fill in the symbol attribute with <component>, <component>_<pin> or
    <component>_<signal>, such as MT47H512M4EB_DQ0 or MT47H512M4EB_C9. As with
    model, the 'spec' keyword can be used.
  * Connect 'Pin' to the outside of the component, 'Gnd' to ground, and the
    third pin to the associated IBIS model.

There is limited support for board description files. If the board description
file only connects from an external pin to internal nodes, it can be used. This
is the case for board description files that describe multiple dies in a single
package. It is done the same way with component pin parasitics except that a
different symbol must be used depending on the number of die pads the along the
path.

Currently unsupported:

  * Driver Schedules.
  * External Models/circuits.
  * ECL.
  * ISSO PU/PD data.
  * Composite current for rising/falling waveforms.
  * Bus hold.
  * Fall back.
  * Series models.

Current limitations:

  * darter.py can generate thousands of subcircuits for some IBIS files,
    ngspice has a hardcoded limit of 1000 subcircuits. I'm not sure if the
    best workaround is to patch ngspice, or modify darter.py to split up its
    output.
  * Output buffers need two rising and falling waveforms each.
  * Open source/sink buffers need one rising and one falling waveform.
  * Ramp data is not used.

PyBIS - Used by darter to parse IBIS files:
http://github.com/russdill/pybis

IBIS Specification:
http://www.vhdl.org/ibis/ver5.0/ver5_0.txt

IBIS Cookbook:
http://www.vhdl.org/ibis/cookbook/cookbook-v4.pdf

Accuracy of IBIS models with reactive loads:
http://www.vhdl.org/pub/ibis/summits/mar06/muranyi1.pdf

A VHDL-AMS buffer model using IBIS v3.2 data:
http://www.eda.org/ibis/summits/jun03b/muranyi1.pdf

IBIS Algorithms Revisted:
http://www.vhdl.org/pub/ibis/summits/jun03a/ross.pdf

Things You Can Learn From V/I Curves:
http://www.eda.org/pub/ibis/summits/jun05/westerhoff.pdf