Hello, Olin Lathrop said that there is a bug with the two level of priorities with the 18F452. I've checked on the Microchip website, and the latest revision they talk about is the B5 one, which still contains the bug. I've sent an e-mail to microchip about C0 revision, but still no response nearly a week later. Somebody who is working with me phoned to Arrow Los Angeles (the company has one office in Belgium, where I am, and one at Los Angeles) to ask about C0, but they didn't know. They said to call Microchip Helpdesk, but even the helpdesk has no information. I've phoned to some distributors in Belgium, but they never have information about the revisions. They asked me about the quantity, if it's a big one, they said, in this case, they can ask Microchip, but only need one or two PIC's How could I get a PIC18F452 without this interrupt bug ? If I order a 18F452, will I have much chance to get one without the bug ? Thanks for your help Laurent Haniken -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.