Re: gEDA: Icarus FF_LPM and Assertions

[Tom Hawkins <tom-at-NOSPAMconfluent_dot_org>]

Stephen Williams wrote:
> Tom Hawkins wrote:
> | I'm almost finished with my Icarus code generator.  Just two more
> | questions:
> |
> | For synthesizable targets, how can the code generator determine if the
> | clock or asynchronous reset for an LPM_FF is sensitive on the positive
> | or negative edge?  I tried a negedge FF, expecting to see a NOT gate
> | dropped into the final netlist, but no such luck.

Any hints for detecting posedge or negedge?  This is my biggest 
roadblock at this point.

> |
> | Also, are there any assertion capabilities built into Icarus?  I'm not
> | sure if there is anything defined in the 2001 spec -- an $assert, maybe?
> |  Ideally what I need is an IVL_LPM_ASSERT block that has similar
> | semantics as IVL_LPM_FF, except without the output data (q).
> 
> Nothing of the sort, sorry. Actually, assertions would be somewhat
> similar (in mechinism, if not appearence) to constraints in specify
> blocks.

Maybe I can get by with some sort of user defined primitive or system 
task.  However, it's not real a high priority item at this point.

> 
> | In case my posts haven't given it away, I'm working on a formal
> | verification plug-in.
> 
> You're going to be angry:-O but it is looking like post-0.8 the
> ivl_target API is going to change some. I'm going to be collapsing
> arrays of pins down to single pins that carry vector data. I'm
> looking towards considerably reducing the size of the netlist
> represented by ivl_target structures, and also allowing pins to
> carry arbitrary data types.

On the contrary, I'm glad to hear this.  Would you consider outside input?

Bill and I have been pondering over an netlist format that could serve 
as the glue between the various open-source tools.  This info is a bit 
dated -- some of my opinions have changed since I wrote this -- but 
here's the general gist:

http://www.confluent.org/wiki/doku.php?id=fnf:main

Everything is open to consideration at this point.

-Tom



> 
> --
> Steve Williams                "The woods are lovely, dark and deep.
> steve at icarus.com           But I have promises to keep,
> http://www.icarus.com         and lines to code before I sleep,
> http://www.picturel.com       And lines to code before I sleep."