Sipke, I haven't seen a lot of other people reply to your request yet, but I will add my two cents on this. I have found that any simulator is going to give you an approximation of what's going to happen. I went through similar problems when I did my code for reading a TV I/R Remote Control. My first version, best case, only had four instruction cycles before the next edge would come in. This turned out to be too close and even though MPSIM indicated that there wasn't any problems, I found a bunch. (Which translates to mean the program couldn't read anything coming through.) My solution was to re-order the program so that I would have 40-50 cycles before the next expected interrupt. At this point, the program worked fine and correlated to the simulator. In the databooks that I have, interrupt latency seems to vary when the edge is received in the instruction timing. This may be what you're seeing here; the simulator doesn't accurately handle at what point the interrupt happens. I don't think this is a Microchip problem, I have seen the same thing on other simulators I have used. The only way you can be absolutely sure that everything will work down to individual instructions is to use an emulator pod (which costs mucho). I have found the best way to ensure your interrupt driven programs work correctly is to leave lots of "space" before and after your expected interrupts. The only analogy I can think of is in terms of Cp and CpK in manufacturing processes. Make sure that your code can handle input irregardless of whether or not the signals come in when you expect. Plot out when you expect them, then give a few instructions on either side and design your program to work right in the middle of that range. Sorry I can't be of more help, Myke >Return-Path: >X-Sender: sdle@ensae >Date: Thu, 28 Mar 1996 14:39:29 +0100 >Reply-To: pic microcontroller discussion list >Sender: pic microcontroller discussion list >From: Sipke de Leeuw >Subject: my mpsim problems >To: Multiple recipients of list PICLIST >X-UIDL: f1ddf1a5569c441a66c2568944079114 > >Hello you all, > >First off all: sorry when this message is sended twice to you. It won't happen >again! > >I am new on the piclist group. I have some trouble with the MPSIM simulator. >A discussion is going on between me and Microchip, but they don't seem to be >able to help me. Can someone help me ?? > >The conversations with Microchip are below ... > Myke "We're Starfleet officers, weird is part of the job." Capt. Catherine Janeway