Post by thread:16F877 xt oscilator problem

Hi PICer friends, I'm using the 16F877 for the first time and I have trouble to start the xt oscillator. the connection on the 16F877 are: vcc - to pin 11 - 32 wired togheter gnd - to pin 12 - 31 wired togheter mclr - to wcc thorught a resistor of 10K xt osc - to pin 13 and 22 pf capacitor to gnd xt osc - to pin 14 and 22 pf capacitor to gnd rb3 - floating (but have been tested connected to the vcc and gnd) the xt are a 4 Mhz quartz Using the blink8x.bas sample program in PBP 2.2 I compile it and I'm able to load the hex into the pic and I can read back the code (that means the PIC is working) but the oscillator do not start. On pin 14 I can see with a scope a stable level of 2,6 volt and on pin 13 a stable level of 2,0 volt . Dear PICer friends, do you have any idea to help me to solve this problem? Ciao Leo For reference purpose you can see the PBP blink8x.bas source: i var byte ' Define loop variable LEDS var PORTD ' Alias PORTD to LEDS TRISD = %00000000 ' Set PORTD to all output loop: LEDS = 1 ' First LED on Pause 500 ' Delay for .5 seconds For i = 1 to 7 ' Go through For..Next loop 7 times LEDS = LEDS << 1 ' Shift on LED one to left Pause 500 ' Delay for .5 seconds Next i Goto loop ' Go back to loop and blink LED forever End

At 09:21 12/11/99 +0100, you wrote: Have you selected the XT oscillator option in the config word? Jim {Quote hidden}>Hi PICer friends, > >I'm using the 16F877 for the first time and I have trouble to start the xt >oscillator. > >the connection on the 16F877 are: > >vcc - to pin 11 - 32 wired togheter >gnd - to pin 12 - 31 wired togheter >mclr - to wcc thorught a resistor of 10K >xt osc - to pin 13 and 22 pf capacitor to gnd >xt osc - to pin 14 and 22 pf capacitor to gnd >rb3 - floating (but have been tested connected to the vcc and gnd) > >the xt are a 4 Mhz quartz > >Using the blink8x.bas sample program in PBP 2.2 I compile it and I'm able to >load the hex into the pic and I can read back the code (that means the PIC >is working) but the oscillator do not start. > >On pin 14 I can see with a scope a stable level of 2,6 volt and on pin 13 a >stable level of 2,0 volt . > >Dear PICer friends, do you have any idea to help me to solve this problem? > > >Ciao > >Leo > > >For reference purpose you can see the PBP blink8x.bas source: > >i var byte ' Define loop variable >LEDS var PORTD ' Alias PORTD to LEDS >TRISD = %00000000 ' Set PORTD to all output >loop: LEDS = 1 ' First LED on >Pause 500 ' Delay for .5 seconds >For i = 1 to 7 ' Go through For..Next loop 7 times >LEDS = LEDS << 1 ' Shift on LED one to left >Pause 500 ' Delay for .5 seconds >Next i >Goto loop ' Go back to loop and blink LED forever >End > Regards, Jim Robertson NEWFOUND ELECTRONICS ________________________________________ Email: spam_OUTnewfoundTakeThisOuTpipeline.com.au http://www.new-elect.com MPLAB compatible PIC programmers. ________________________________________

Leo wrote: >Dear PICer friends, do you have any idea to help me to solve this problem? I had some startup trouble with an '877 and a 4MHz ceramic resonator from Murata. Increasing the configuration bit to HS helped (higher drive from the PIC) but I didn't like that. A look at Murata's website suggested a 1M resistor across the resonator, so I tried that and I haven't had any trouble since. I assume the same trick with crystal would work, it's worth a try. Dave Johnson

Hi Mike, thanks for your suggestion. Ciao Leo ----- Original Message ----- From: Myke Predko <.....mykeKILLspam@spam@PASSPORT.CA> To: <PICLISTKILLspammitvma.mit.edu> Sent: sabato 13 novembre 1999 16.47 Subject: Re: 16F877 xt oscilator problem > Hi Leo, > > Your problem is that you aren't disabling the "LVP". Specify "_LVP_OFF" in {Quote hidden}> your "__CONFIG" Statement and everything will run fine. > > I had the same problem a few weeks ago. > > myke > ----- Original Message ----- > From: Leo <.....cacciaviteKILLspam.....BIGFOOT.COM> > To: <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> > Sent: Friday, November 12, 1999 3:21 AM > Subject: 16F877 xt oscilator problem > > > > Hi PICer friends, > > > > I'm using the 16F877 for the first time and I have trouble to start the xt {Quote hidden}> > oscillator. > > > > the connection on the 16F877 are: > > > > vcc - to pin 11 - 32 wired togheter > > gnd - to pin 12 - 31 wired togheter > > mclr - to wcc thorught a resistor of 10K > > xt osc - to pin 13 and 22 pf capacitor to gnd > > xt osc - to pin 14 and 22 pf capacitor to gnd > > rb3 - floating (but have been tested connected to the vcc and gnd) > > > > the xt are a 4 Mhz quartz > > > > Using the blink8x.bas sample program in PBP 2.2 I compile it and I'm able > to > > load the hex into the pic and I can read back the code (that means the PIC > > is working) but the oscillator do not start. > > > > On pin 14 I can see with a scope a stable level of 2,6 volt and on pin 13 > a > > stable level of 2,0 volt . > > > > Dear PICer friends, do you have any idea to help me to solve this problem? {Quote hidden}> > > > > > Ciao > > > > Leo > > > > > > For reference purpose you can see the PBP blink8x.bas source: > > > > i var byte ' Define loop variable > > LEDS var PORTD ' Alias PORTD to LEDS > > TRISD = %00000000 ' Set PORTD to all output > > loop: LEDS = 1 ' First LED on > > Pause 500 ' Delay for .5 seconds > > For i = 1 to 7 ' Go through For..Next loop 7 times > > LEDS = LEDS << 1 ' Shift on LED one to left > > Pause 500 ' Delay for .5 seconds > > Next i > > Goto loop ' Go back to loop and blink LED forever > > End > >