Re: Compilation question

Shalom -
There is perhaps a difference in understanding of what "compilation"
means.  In the Verilog-A compact modeling world, we have these
very complicated modules that get "compiled" from Verilog-A to
C and then to object code that is dynamically linked into the
simulator.  This is somewhat different from the "compilation"
that I think digital Verilog simulators do when they set up
a particular netlist to run (and run quickly).

LRM 2.2 does, indeed, have that paragraph -- taken directly
from 1364-1995 (section 3.10).  All the analog simulators
I've used take that with a nudge and a wink and allow the
parameter value to be changed.  Of course, since the 1364
LRM doesn't know what a "dc sweep" is, one could argue that
a "dc sweep" is really a set of runs, in each of which the
parameter value is constant.  I believe there are open issues
for Verilog-AMS about cleaning up the mixed-signal initialization
and fully explaining what a "dc sweep" means.

-Geoffrey


"Bresticker, Shalom" wrote:
> 
> On the contrary, the 2.2 LRM says,
> 
> "Parameters represent constants, hence it is illegal to modify their
> value at runtime. However, parameters can be modified at compilation
> time to have values which are different from those specified in the
> declaration assignment. This allows customization of module instances. A
> parameter can be modified with the defparam statement or in the
> module_instance statement."
> 
> A -defparam on the command line is just a substitute for a defparam
> statement in the code. It is still evaluated at compilation time.
> 
> You should have some basic understanding of what compilers do.
> Among others things, compilers translate the source code into a data
> structure. Changing the data structure requires a recompilation. It may
> be an incremental recompilation, but a recompilation nevertheless.
> 
> There might be special cases of parameters which you could change
> without requiring a recompilation, such as a transistor value, but that
> is not changing the data structure.
> 
> Shalom