This directory provides an example of how "black box" subcircuits work.
The more involved example is in dll.c and is a dll simulation.
To see what it does make irsim.user and then run it on 
dll.sim with dll.cmd. The edges of the two clocks should be aligned
by the end of the simulation and the updn signal should be switching.

The subcircuit is called by:

 x upDn inClk outClk outClk1 dll

it means call the subcircuit dll (defined in dll.c) with inputs
(upDn, inClk, outClk) and output (ouClk1).

To create and compile a new subcircuit library, replace "user.c" in
the Makefile with the source file containing the library initialization
and evaluation routines.  The files "dll.c" and "flop_mux.c" are provided
as examples.

Some caveats:
1. The output delay is always specified in picoseconds.
2. You might have to change the MAXARGS in sim.c to if you have way too many IO's.
3. The code in this directory is deprecated and has been replaced by the
   example code in directory "tclsubckt", which allows subcircuit libraries to
   be compiled and loaded independently of irsim.
