The ONLY complete way I know to reset a '51 is to time a watchdog out. Yes, multiple RETIs etc will get the interrupt reset, but what about the SFRs. Once I did it, I went through the SFR list for the processor in question and coded that upon reset they all got set to their initial state. After a lot of debugging, I found that I had to rearrange the sequence to obtain a true reset. Yes, eventually it worked, but since then I have adhered to the first statement in this post.

Erik