Automatic Program Suspension by SIMPLIS

Sometimes the input circuit may contain a switching conflict which SIMPLIS cannot resolve. For example, connecting the input and output nodes of a SIMPLIS inverter together creates a situation where the inverter cannot locate a valid logic output state from which to operate. Once such a switching conflict occurs, the simulation enters an endless loop and it is unable to advance forward in time. After attempting 200 times without any success in locating a correct operating state, SIMPLIS prints a message to the message window similar to the following, and aborts the simulation:

Unable to find a starting operating point

At t = 1.2345e-06, it is unable to find the correct state of
operation for some device.
For example, check the following devices:
!R1, !R2, and !R3

If such a message appears, you should carefully inspect the input file and appropriate data files generated by SIMPLIS to locate the source of the switching conflict. In a slightly different scenario, the situation may occur when the switching logic is properly defined but a few circuit elements are connected in a manner which may cause the simulation to go through very fast and repetitive switching in a small group of states. If the time interval between two switching events is so short to be negligible compared to the actual simulation time variable, SIMPLIS aborts the simulation and displays a similar message to the following:

No advance in the time variable
at t = 3.1425e-05 sec.

This example error message means that when the time variable, t, reaches 3.1425x10 -5 sec in the simulation, two consecutive switching events have occurred within a time span that is negligible compared to 3.1425x10 -5 sec. A number is considered to be negligible to another number if it is sixteen orders of magnitude below the larger number. Again, you should then inspect the input file and appropriate data files generated by SIMPLIS to locate the source of the problem.