Logging AET Results for 4 Value Simulation

Logging AET Results for 4 Value Simulation

      Disclosed is a solution for logging AET (All Events Trace)
results for 4 value simulation.  Not only will it record the 2 value
simulation states 0 and 1, it will record 2 additional states.  These
states are X (unknown), and H (high impedance).

      To log AET results for 2 value simulation, the format for
logging AETs used by CEFS (Compiled Enhanced Functional Simulator), a
2 value simulator, was acceptable.  This consists of the records
described below.  The record header code (in parentheses) indicates
what type of record follows.
      -    Header Data Record (E0), contains the date and time of
simulation.
      -    AET Mask Record (E9), contains the location in Complete
State Record to find net to be logged.
      -    Complete State Record (E1), contains the entire bit string
for this state of a 2 cycle simulation.
      -    AET Time Record (E6), contains the number of clocks since
simulation began.
      -    Changed Value Record (E4), contains a log of only the
values of nets which have changed since the last clock.
      -    Simulation Reset (E7E8), just an indication that the
simulation was reset.  Nothing is logged except the record header
code (E7E8).
      -    AET Stop Record (6F), indicates the end of AET logging.

      In order to log results for 4 value simulation a new record was
added (E2).  This record contains the Complete St...