Thankyou to all that replied to my post it has been most helpful. The difference between the oscilator accuracy for the 16f628 & the 16f628A is very interesting indeed. Upon closer inspection I note that the chip is in fact the 16f628A. I think maybe my problem lies somewhere else, maybe the variables are getting messed up inside the chip before being transmitted back. It only occured to me later but I have been getting reliable comms at 250K (yes 250,000bps) using a 28A on another project with internal osc but that was with RS285 and SN75176 drivers/receivers. Regards, Lee. ----- Original Message ----- From: "William Chops Westfield" To: Sent: Saturday, January 03, 2004 11:26 AM Subject: Re: [PIC]:RS232 Communications Reliability With PIC16F628 > On Friday, Jan 2, 2004, at 04:31 US/Pacific, Olin Lathrop wrote: > > > > > Lee Wright wrote: > >> I'm having trouble with a PIC16F628 sending data @ 2400 baud and > >> using internal OSC. > > > > That's not surprising, since the oscillator can be up to 8.75% off and > > 5.8% > > is the guaranteed to fail limit of RS-232 for 8 data bits. > > > > > heh. Is it really a 16F628, or a 16F628A? This seems to be one of the > big > changes between the two, with the A version proudly proclaiming a 1% > accurate > intosc (still better than 5% over voltage and temp ranges, according to > the > data sheet.) I guess they got (rightfully) yelled at for making an > internal > oscillator that wasn't accurate enough for serial comm... > > BillW > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics