Use EEPROM write timing to distinguish instead of WDT. Keep trying until you get different values. start write while write in progress increment 8 bit counter end while This is less hassle than dealing with the WDT since it doesn't require letting a reset happen. Bob Ammerman RAm Systems ----- Original Message ----- From: "John Nall" To: Sent: Monday, June 09, 2003 4:38 PM Subject: Re: [PIC]: Deciding who is master > At 12:22 PM 6/9/2003 -0400, you wrote: > > >Design the PCB so that one line (TX to RX) has a pull up resister, the > >other (RX to TX) having a pull down resister. > > But....perhaps I am missing something...but it seems to me that the two > PCB's would have a conflict in that case. Call them A and B. Then Tx(A) > connects to Rc(B). So the line that A sees as Tx to Rc is the exact same > line that B sees as Rc to Tx. A pull up which affects Tx(A) also affects > Rc(B) because they are connected. Ditto with a pull down. No?? > > BTE, I've had some very original and creative ideas come back, but some of > them seem to ignore the two primary prerequisites: (1) The two PCB's are > identical, and are turned on with a common power supply, and (2) The > software (OK, firmware) in them is also identical. It does not matter > which is master and which is slave, just so long as it is done. It may > not be the same each time the system is powered on (although I suspect it > will be the same). > > The suggestions that say "Have A check so-and-so and then do thus and > thus..." seem to forget that between the time A does the check and the > time A does something, B can also make the check, and make the exact same > assumption. Unfortunately, there is no single instruction that says "check > and change". :-) > > I don't want to seem ungrateful, though, and am not. Some of the ideas are > really good ones and I am very appreciative of the responses. > > John > > -- > 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