The chance of 2 chips being faulty seems kind of low, so possibily still so= me other issue. Could still be in the config bits... programmed at the time= the bootloader is loaded and can't be changed thereafter (pretty sure PIC = can't self write config bits). You can probably read those back with a prog= rammer, but if the config bits aren't right the programmer itself becomes a= suspect. Good that flags show a reset is happening (which almost certainly explains = the symptoms). You can probably go further and deduce if it was from WDT re= set or something else. On the other hand, your "it is what is" comment coul= d indicate you're ready to move on. Understood. Less than 12hrs to Christma= s here~! -------- Original message -------- From: andrew kelley =20 Date: 12/23/17 5:07 PM (GMT+12:00)=20 To: "Microcontroller discussion list - Public." =20 Subject: Re: [PIC]: 18f2550 timer 1 interrupt glitch?=20 Checked reset flags, seems like a reset instruction is being executed, but there isn't one in the code. I'm thinking both these 2550s are faulty, considering the Exact Same Code runs perfect on one of my 4550 boards. I haven't any idea why it would be that way, but it is what it is and that's all it is. Thanks for the help Andrew --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .