Jeff, a not well handled subroutine (a return without a call) could do wh= at you talk about. =20 Also, a not well handled ISR subroutine (the environment data not well = saved and restored) can produce that. =20 I wouldn't search on the hardware on the first place. =20 =20 Some simple software run well on a couple of simulation cycles. Some = bugs come with seconds of operation! Where million of instructions are e= xecuted and so... more chances to get a problem on a buggy code (althoug= h at the first sight seems ok). =20 =20 "Anno, Jeff" escribi=F3: Hey Piclisters, I'm having some flaky results with RS232 Communication on the Pic 16F877A= . =20 I suspect it is a grounding issue because I can change the results by touching the cable shield (9 pin D Shell). =20 After some short settling time, the chip sends "Power On" text to the por= t at 9600 Baud. In Hyper terminal I can see this message at power up. I c= an also tell that it is receiving correctly because it reports "channel 1" w= hen I send it a "1" and "Channel 2" when I send it a "2", etc... So I suspect that the code is working. =20 Occasionally it appears that the chip has 'reset' because I get the "Powe= r On" text appearing when I haven't unplugged it. It would also stop reporting "Channel X" when I would send it "X". I could wiggle and touch the cable and it would start working again after the power on message. I am powering it through a wall wart (8 V DC) and then across a 5V regula= tor (also tried a linear DC Power Supply). I have tried two different chips = to ensure that it wasn't an individual chip problem. The chip had given the flaky results when it was on my bread board, so I made a circuit board an= d still had the same flaky communication. I have Pin 5 going to ground, Pi= ns 2 & 3 going to the RS232 chip (tried Maxim 232CPE and Sipex 232ACP). I ha= ve tried connecting the shield to ground and got a reset each time. I have = the five 1uf electrolytic caps for the rs232 chips with the right polarity (triple checked). I even connected pins 1, 4, & 6 together as well as 7 & 8. Nothing I have tried helps. The cable is the same cable that I program the chip with, s= o I don't see any issues with it either. Any Suggestions???? Thanks in advance, Jeff Anno --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =09 --------------------------------- 1GB gratis, Antivirus y Antispam Correo Yahoo!, el mejor correo web del mundo Abr=ED tu cuenta aqu=ED --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist