Information/specification -- LXT2 format

[Harish Sundararaj]

Hi all,

LXT format is soimetime used to describe wave forms. LXT2 format is a
format with certain enhancements over LXT..(though not sure what
exactly they are.). I need the format specification for LXT2(or atleast
some information on LXT2 format). The gtkwave page gives documenation
only for LXT format.

Thanks in advance,
Rgds
Harish

 

Harish Sundararaj wrote:

LXT format is soimetime used to describe wave forms. LXT2 format is a
format with certain enhancements over LXT..(though not sure what
exactly they are.). I need the format specification for LXT2(or atleast
some information on LXT2 format). The gtkwave page gives documenation
only for LXT format.

Outside of how signal names and geometries are stored, LXT and LXT2 are
completely different dumpfile formats.

In a nutshell:

1) LXT2 is a block-based format in order to allow some amount of random
access. Partial loading of blocks is possible if it is turned on
during writing.
2) In order to aid in compression, the writer compares the previous vs
current value for a net in order to see if there is some quick and
simple mathematical way of representing the difference. (e.g., +/-1,
invert, left/right shift, etc)
3) Because of the delta compression of (2), the internals of individual
blocks need to be processed sequentially.

The block format is rather complex and I haven't gotten around to
documenting it. I suggest you stick with the API reader/writer
functions unless your intent is to write your *own* dumpfile format. If
so, looking at the writer sourcecode will be much easier than the
reader sourcecode as all the block writes more-or-less take place in
the single function lxt2_wr_flush_granule().

-t