.tran resolution

In a .tran command like “.tran 500u 10n” the variation of tstop does not seem to be taken into account, it is always 1n.
With the addition of tstart in .tran like “.tran 0 500u 100u 1n” the passage of tstop from 1n to 0.1n is well taken into account.
What is the way to use .tran?
Thank you for your help.

QSPICE is correct here, or at least working as intended.

It deals with the fact the Berkeley SPICE used to only do plots on paper printers with ASCII characters. The first number after .tran was the time between print plotted points and the second number was the amount of time to simulate. A minimum of two numbers were required. Time between plotted points and then for so much time was a natural way to read the command.

But, if there’s only one number on the .tran, then that is used as the stop time, since it’s unambiguously not the original Berkeley SPICE syntax.

But other than that, QSPICE follows the original Berkeley syntax.

The help file clearly documents the two forms of .tran syntax.

Maybe it’s time to drop support for the Berkeley syntax.


Thank you so much for your answer.