Post by thread:[PICLIST] PIC: F877 Wont Start

part 0 44 bytes his is a multi-part message in MIME format. part 1 2562 bytes content-type:text/plain; charset=us-ascii (decoded 7bit) Below is the source code to a simple program to lite some LEDs. Original description of problem is at bottom of this message. Since the original message I can confirm the following: The DC voltage on the CLK-OUT pin is about 2.2 Volts The AC voltage on the CLK-OUT pint is about 5 Volts. The crystal is 20MHz with 2 x 15pf caps. There is a current limiting resistor of 470 ohm connecting the xtal to the CLK-IN pin. I have a 10K pullup resistor on the -MCLR pin. +5 Volts is connected to both supply pins on the chip GND is connected to both GND pins on the CHIP. I have a de-coupling cap 0.01uF close to the chip between +5 and GND. The power supply is fine - it operates other PICs for me without trouble. As originally stated: I can program the chip without problems but it appears not to run at all. Simple program below will not lite the LED's on PORTB. I have used an 'F84 with same/similar program and it works fine. I am concerned that I have "killed" the 'F877 through not protecting it from static when handeling. I include a PDF of the listing file from MPASM. Thanks so far for your help, but I am still lost here. Regards, Shane ********************************* list p=16f877 ; list directive to define processor #include <p16f877.inc> ; processor specific variable definitions __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _WRT_ENABLE_OFF & _LVP_OFF & _DEBUG_OFF & _CPD_OFF RESET_VECTOR ORG 0x000 ; processor reset vector goto main ; go to beginning of program ORG 0x005 main clrf STATUS movlw 0xFF ; turn on all the LEDs movwf PORTB bsf STATUS, RP0 ; goto bank 1 clrf TRISB ; setup for output bcf STATUS, RP0 ; back to bank 0 goto $ END ******************************************** Original Message below ******************************************** > I am new to the PIC world but I do have some experience with computer hardware and software. > > I have built a very basic 'F877 with the minimum support components running at 20MHz. > > I can program the device without any trouble but the CPU appears not to do anything. I don't have > any test equipment other than a good multimeter. > > I can measure about 2.5VDC on the clock pin - so I assume the oscillator is running. Other voltages > all look fine. part 2 8627 bytes content-type:application/pdf; (decode) part 3 105 bytes -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Shane Bolton wrote: {Quote hidden}> > list p=16f877 ; list directive to define processor > #include <p16f877.inc> ; processor specific variable definitions > > __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & > _WRT_ENABLE_OFF & _LVP_OFF & _DEBUG_OFF & _CPD_OFF > > RESET_VECTOR ORG 0x000 ; processor reset vector > goto main ; go to beginning of program > > ORG 0x005 > main > clrf STATUS > > movlw 0xFF ; turn on all the LEDs > movwf PORTB > > bsf STATUS, RP0 ; goto bank 1 > clrf TRISB ; setup for output > bcf STATUS, RP0 ; back to bank 0 > goto $ > Try this simple code which should flash a LED connected to RB0. The LED should be in series with a 2K2 resistor to ground. Notice the other ports are initialised and set as outputs because they are not connected to anything. Floating inputs can cause all sorts of havoc. list p=16f877 ; list directive to define processor #include <p16f877.inc> ; processor specific variable definitions __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _WRT_ENABLE_OFF & _LVP_OFF & _DEBUG_OFF & _CPD_OFF CBLOCK 0x20 NaHi NaLo NbHi NbLo ENDC RESET_VECTOR ORG 0x000 ; processor reset vector goto main ; go to beginning of program ORG 0x005 main clrf PORTA ; all pins = low clrf PORTB clrf PORTC clrf PORTD clrf PORTE bsf STATUS,RP0 ; RAM Page 1 clrf TRISA ; all pins = outputs clrf TRISB clrf TRISC clrf TRISD clrf TRISE ; ; ------------------------- ; SET ANALOG/DIGITAL INPUTS = all digital ; ------------------------- ; movlw 06h movwf ADCON1 bcf STATUS,RP0 ; RAM Page 0 ; ; -------------- ; MAIN CODE LOOP ; -------------- ; Loop bsf PORTB,0 ; turn a LED on call Delay ; wait a bit bcf PORTB,0 ; turn a LED off call Delay ; wait a bit goto Loop ; keep doing this loop ; ; 1/2 sec DELAY SUBROUTINE @4MHz ; 100mS @ 20MHz ; Delay movlw 01h movwf NbHi movlw 03h movwf NbLo movlw 8Ah movwf NaHi movlw 5Bh movwf NaLo DeLoop0 decfsz NaLo,F goto DeLoop0 decfsz NaHi,F goto DeLoop0 decfsz NbLo,F goto DeLoop0 decfsz NbHi,F goto DeLoop0 return end -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam@spam@bubblesoftonline.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

Found the problem!! I pulled the chip out and put it in a breadboard. put new caps, crystal, pullups and hooked it up to a power supply. Works fine. I then replaced the chip into the board and started to change components. First the Crystal Caps - no joy. Then the crystal - FIXED. I can't explain this, as it appeared that the crystal was running (5 VAC on the CLK-OUT pin) but obviously something was wrong. I did not even re-program the chip - it worked fine. Considering my total lack of concern for Static protection etc. these PICs sure are tough!!! Just like to say thanks to everyone that responded with suggestions - a very helpfull and co-operative list. Shane Bolton Shane Bolton wrote: {Quote hidden}> > Below is the source code to a simple program to lite some LEDs. Original description of problem is > at bottom of this message. > > Since the original message I can confirm the following: > > The DC voltage on the CLK-OUT pin is about 2.2 Volts > The AC voltage on the CLK-OUT pint is about 5 Volts. > > The crystal is 20MHz with 2 x 15pf caps. There is a current limiting resistor of 470 ohm connecting > the xtal to the CLK-IN pin. > > I have a 10K pullup resistor on the -MCLR pin. > > +5 Volts is connected to both supply pins on the chip > GND is connected to both GND pins on the CHIP. > > I have a de-coupling cap 0.01uF close to the chip between +5 and GND. > > The power supply is fine - it operates other PICs for me without trouble. > > As originally stated: I can program the chip without problems but it appears not to run at all. > Simple program below will not lite the LED's on PORTB. I have used an 'F84 with same/similar > program and it works fine. > > I am concerned that I have "killed" the 'F877 through not protecting it from static when handeling. > > I include a PDF of the listing file from MPASM. > > Thanks so far for your help, but I am still lost here. > > Regards, > > Shane > ********************************* > > list p=16f877 ; list directive to define processor > #include <p16f877.inc> ; processor specific variable definitions > > __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & > _WRT_ENABLE_OFF & _LVP_OFF & _DEBUG_OFF & _CPD_OFF > > RESET_VECTOR ORG 0x000 ; processor reset vector > goto main ; go to beginning of program > > ORG 0x005 > main > clrf STATUS > > movlw 0xFF ; turn on all the LEDs > movwf PORTB > > bsf STATUS, RP0 ; goto bank 1 > clrf TRISB ; setup for output > bcf STATUS, RP0 ; back to bank 0 > goto $ > > END > ******************************************** > Original Message below > ******************************************** > > > I am new to the PIC world but I do have some experience with computer > hardware and software. > > > > I have built a very basic 'F877 with the minimum support components running > at 20MHz. > > > > I can program the device without any trouble but the CPU appears not to do > anything. I don't have > > any test equipment other than a good multimeter. > > > > I can measure about 2.5VDC on the clock pin - so I assume the oscillator is > running. Other voltages > > all look fine. > > ---------------------------------------------------------------------------------------------------- > Name: basiclst.PDF > basiclst.PDF Type: Portable Document Format (application/pdf) > Encoding: base64 -- -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Crystals are glass and can be broken if dropped. It's also possible to damage them if you clip the leads with diagonal cutters (the shock goes up the lead). But also, crystals can oscillate in an overtone (harmonic) which would give you too high a frequency (that's the reason for the capacitors, I hear). Finally, with the oscillator's higher gain settings, the circuit will likely oscillate on its own even without a crystal so if the crystal is broken it may still oscillate...somewhere... Oh, put []'s around the PIC: and I bet a lot more people will see your message! Barry At 10:31 AM 6/29/01 +0530, you wrote: >Yeah, thats the most plausible explanation for > Shane Bolton's Crystal Paradox(Don't I sound ridiculous ?) > Anybody else has got a better theory ? > >Jeethu Rao > > >{Original Message removed}