Win MPLAB has an excellent simulation which I use all the time. It can be run, single stepped, or run slowly so that you can just about follow the changes in register and port values. If there are too many registers changing at once you might miss some. I overcome that by inserting a break just before the busy section and using single step. Brian -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Engineering Department Sent: 16 September 1998 14:20 To: PICLIST@MITVMA.MIT.EDU Subject: PIC16c5X simulators Is there a PIC16C5X DOS or Windoze simulator (not ICE) available to single step etc. through an assembly program as a code check? Thanks, Win Wiencke Image Logic Corporation ImageLogic@ibm.net