Summary
- The user selects the preferred mode at run time based on a description of the implementation capabilities.

- Allow the implementation to support a number of different modes
	2-state mode only (strict) – report error if X/Z passed to emulator 
		This is the minimum supported mode and the default mode.
	2-state mode with selectable coercion 
		User specifies coercion mapping (X = 0/1;  Z=0/1) 
		User specifies if warning is issued for X/Z in this mode or not 
	4-state mode (no coercion) 
- Allow the user to query the implementation capabilities at initialization time.
- Allow the user to select the preferred mode of implementation operation after the query.
- Allow the user to select the preferred mode of TB.
- Selecting an unsupported mode results in an error.
- Question:   Do we allow an implementation to support only two-state types at run time?

New Calls
- Update SCEMIInit, to take an argument, or add a new call SCEMICapabilities.
	SCEMIInit(struct SCEMICapabilities *e);   or
                SCEMIQueryCapabilities(struct SCEMICapabilities *e);
- The SCEMICapabilities structure has one member, StateSupport, an enumerated type.
- Add SCEMISelectCapabilities(const SCEMICapabilities *e,int XValue, int YValue);
	This selcets mode and coercion.


Usage example pseudocode:
SCEMIInit(SCEMICapabilities &e);
if( e.StateSupport == FullFourState) {
  request full four state;
  set TB mode to four state;
} else if (e.StateSupport == FourStateTypesWithCoercion) {
  Specify coercion X/Z to (0,1)
  set TB mode to two state;
} else if (e.StateSupport == TwoStateStrict) {
  set TB mode to strict two state
} else if (e.StateSupport == TwoStateTypesOnly ) {
  Set TB mode to two state only mode
} else {
  /* this should have been detected at compile time  - ie. 2 state minimum is required */
  throw("compiled against the wrong library");
}


 

Note:  As per your modification, at run time, the emulator is queried at init for its capabilities (hidden to user in middleware/rendezvous)

 

-          if the user mode selected fits within the capability of the emulator -> accepted

-          if the user mode selected does not meet the emulator’s capability -> error @ init time

            

Example:

 

-          Emulator capable of 2-state, with or without coercion

 

Case 1:

-          User selects:  4-state (no coercion)

-          Emulator will report error

 

Case 2:

-          User selects:  2-state (coercion), mapping X=0, Z=1, no warning

-          Emulator accepts and runs without warning