You need to be more specific: What kind of output - sine wave, square wave, etc. What kind of precision (ie: granularity of output frequencies). How close together do the frequencies have to be? Does this closeness figure vary with higher frequencies? What kind of accuracy? When you tell it to generate 154Hz, what error is allowable? What kind of repeatability? If you tell it to do 154Hz today, and tell it again tomorrow, how much difference is allowable? What kind of stability? If you tell it to do 154Hz and leave it in that mode for 10 minutes how much is it allowed to drift. Note: Answers of 0 to any of the above questions regarding error limits will make your device impossible to build. In many ways costs are inversely proportional to allowable errors. Finally, direct generation of signals above the audio range with any kind of precision is going to be difficult with a bare PIC. Bob Ammemran RAm Systems ----- Original Message ----- From: "Joe Farr" To: Sent: Tuesday, June 04, 2002 4:11 AM Subject: [EE]: Frequency stability of a PIC Hello all. A general question that I hope some of you more 'seasoned' PIC people can answer. I need to construct a variable frequency generator. Capable of producing frequencies from a couple of Hz up to around say 1 or 2 Mhz. The accuracy has to be spot on and I mean spot on. If the display say 154Hz then it must be 154Hz and be capable of this for about 10 mins at a time. No glitches whist the PIC runs off to service some interrupt or other housekeeping task. In theory, the code 'feels' quite simple to write. However, do you believe that the PIC hardware is up to the task Don't really have any preference of which PIC to use. I'm a 16F877 man, so would probably opt for this unless you feel a different choice would be best. Any insights would be very helpful. Thanks, Joe. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body