Hi Mark I was just notified by the rep for Murata (they make the 4 MHz resonator I'm currently using) that they have a resonator that is 7.3728MHz so I'm good to go with my current part. I just need to order the different parts and tweak the timing of things to account for the faster clock. I will likely migrate eventually to the 18F6622 or some other device in the family. (Seems like when I was working on a multiple ISR issue where when I loaded some ISRs high and some low gave me problems. I tried one of those parts to see if the ISR issue was a silicon problem and it turned out to have a silicon error with the CCP not being able to use the I/O pins I had chosen.) Thnaks again for the help. Phillip Things should be as simple as possible but no simpler Phillip Coiner CTO, GPS Source, Inc. Your source for quality GNSS Networking Solutions and Design Services, Now! -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Mark Rages Sent: Wednesday, May 30, 2007 1:29 PM To: Microcontroller discussion list - Public. Subject: Re: [PIC] 18F6620 baud rate generator On 5/30/07, Phillip Coiner wrote: > Hi Brent & Jinx > > Thanks for the spread sheet (Brent) and the formula (Jinx). > Till I can get a different crystal purchased and installed (actually I'm > using a Murata resonator I might have to change a foot print on my board). > I wanted to use my 4MHz crystal but when I set the BRGH 1(Low Speed) and run > through the math I end up with a %8.51 error. > Can anyone tell me if that is close enough to work for now so I can test my > code? > 18f6620 is not recommended for new design. its more modern replacement, the 18f6622, has a better baud rate generator. In particular, it has a BRG16 bit. With a 4MHz oscillator, it can do 111111 baud. This is 3.5% error, which is close enough. (I wouldn't design a real product with this much error though -- if the tolerances add up the wrong way it might quit working.) See the last line of table 20-3 in the datasheet. Regards, Mark markrages@gmail -- Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist