Post by thread:[PIC]:16F873 PortC bit 5 revisited

Dear PicList - I sent this email out yesterday asking why, or what I am doing that would cause port c bit 5 to be pulled low internally to the chip. The ensuing discussion has branched off to my use of using bcf, bsf to toggle a bit on and off in order to get a feel for what the PIC was seeing - this may or may not be proper code - it was just there for test purposes. As to why bit 5 is hung low - not an educated - or even uneducated guess. As I told my wife - I feel sort of like a guy who jumps out of an airplane - his chute does not open and he radios for help. The people on the ground get into a long winded discussion about what kind of handle he has on his rip cord and why it should be something else - never addressing the real problem. Sorry if I sound aggravated - I guess I was really hoping someone had the answer as to why bit 5 is being held low instead of seeing discussion on my use of bcf, bsf. Thanks to all, David Since my last post, I have simplified my code to almost nothing to try to find out why my 16F873 wants to pull port c bit 5 low - the code is below. In this case I set port c up then input port C, check to see if bits 0,1,4 or 5 are low (they are pulled up to 5v by a 220 ohm resistor - pulling them down is by a momentary push button switch). If one of the inputs is low the code determines which one and jumps to code that then pulses port c bit 3 either 1, 2, 3 or 4 times to indicate which button is pressed. I then can observe the output bit via my oscilloscope. When the code runs in my emulator all is well. But when I burn a 16F873 and place it in the circuit the output shows 4 pulses without a button being pushed - sure enough bit 5 is low on the oscope. Pull the 16f873 from the circuit and the pin goes high. Something internal to the 16f873 is causing port c bit 5 to be low (over riding the 220 ohm resistor). The only peripheral I can find on the 16f873 that shares port c bit 5 is the Sync Serial Port, but I feel that I have disabled it. If anyone has any hints, I sure would be happy to hear them! Thanks, David include 'c:\ptools\16f873.inc' Fuses _CP_OFF Fuses _DEBUG_OFF Fuses _WRT_ENABLE_ON Fuses _CPD_OFF Fuses _LVP_OFF Fuses _BODEN_OFF Fuses _PWRTE_ON Fuses _WDT_OFF Fuses _HS_OSC TEMP_B equ 078h ;temporary register org 0000h START INIT_PORTS bsf RP0 ;point to bank 1 bcf RP1 ; movlw 10110011b ;set port c to 7->Rx, 6->Tx, 5->Dim, 4->Bright movwf TRISC ;3->test out, 2->PWM, 1-> Zero, 0->Hold/Cont movlw 00h ;load 0 into W movwf SSPCON2 ;then into Sync Ser Port Cont 2 movwf PIE1 movwf PIE2 bcf RP0 ;point to bank 0 movlw 00h ;load 0 into W movwf PIR1 movwf PIR2 movwf SSPCON ;then into Sync Ser Port Control MAIN movf PORTC, W ;read port C into W movwf TEMP_B ;and into TEMP_B andlw 00110011b ;mask off key bits xorlw 00110011b ;any bits low? btfsc Z ;if key pressed then skip goto MAIN ;else jump btfss TEMP_B,0 ;if Hold/Cont not set then jump goto SCAN_H:C ;else jump btfss TEMP_B,1 ;if Zero not set then jump goto SCAN_ZERO ;else jump btfss TEMP_B,4 ;if Brighten not set then jump goto SCAN_BRIGHT ;else jump btfss TEMP_B,5 ;if Dim not set then jump goto SCAN_DIM ;else jump goto MAIN SCAN_H:C bsf Portc,3 ;port C bit 0 low bcf portc,3 ;so pulse bit 3 once goto MAIN SCAN_ZERO bsf Portc,3 ;port C bit 1 low bcf portc,3 ;so pulse bit 3 twice bsf Portc,3 bcf portc,3 goto MAIN SCAN_BRIGHT bsf Portc,3 ;port C bit 4 low bcf portc,3 ;so pulse bit 3 three times bsf Portc,3 bcf portc,3 bsf Portc,3 bcf portc,3 goto MAIN SCAN_DIM bsf Portc,3 ;port C bit 5 low bcf portc,3 ;so pulse bit 3 four times bsf Portc,3 bcf portc,3 bsf Portc,3 bcf portc,3 bsf Portc,3 bcf portc,3 goto MAIN end David V. Fansler S/V Annabelle spam_OUTDFanslerTakeThisOuTMindSpring.com http://www.dv-fansler.com -- 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

At 10:59 PM 03/04/2002 -0500, you wrote: {Quote hidden}>Dear PicList - I sent this email out yesterday asking why, or what I am >doing that would cause port c bit 5 to be pulled low internally to the chip. >The ensuing discussion has branched off to my use of using bcf, bsf to >toggle a bit on and off in order to get a feel for what the PIC was seeing - >this may or may not be proper code - it was just there for test purposes. >As to why bit 5 is hung low - not an educated - or even uneducated guess. >As I told my wife - I feel sort of like a guy who jumps out of an airplane - >his chute does not open and he radios for help. The people on the ground >get into a long winded discussion about what kind of handle he has on his >rip cord and why it should be something else - never addressing the real >problem. Sorry if I sound aggravated - I guess I was really hoping someone >had the answer as to why bit 5 is being held low instead of seeing >discussion on my use of bcf, bsf. > >Thanks to all, >David > >Since my last post, I have simplified my code to almost nothing to try to >find out why my 16F873 wants to pull port c bit 5 low - the code is below. >In this case I set port c up then input port C, check to see if bits 0,1,4 >or 5 are low (they are pulled up to 5v by a 220 ohm resistor - pulling them >down is by a momentary push button switch). If one of the inputs is low the >code determines which one and jumps to code that then pulses port c bit 3 >either 1, 2, 3 or 4 times to indicate which button is pressed. I then can >observe the output bit via my oscilloscope. When the code runs in my >emulator all is well. But when I burn a 16F873 and place it in the circuit >the output shows 4 pulses without a button being pushed - sure enough bit 5 >is low on the oscope. Pull the 16f873 from the circuit and the pin goes >high. Something internal to the 16f873 is causing port c bit 5 to be low >(over riding the 220 ohm resistor). The only peripheral I can find on the >16f873 that shares port c bit 5 is the Sync Serial Port, but I feel that I >have disabled it. > >If anyone has any hints, I sure would be happy to hear them! >Thanks, >David > > > include 'c:\ptools\16f873.inc' > Fuses _CP_OFF > Fuses _DEBUG_OFF > Fuses _WRT_ENABLE_ON > Fuses _CPD_OFF > Fuses _LVP_OFF > Fuses _BODEN_OFF > Fuses _PWRTE_ON > Fuses _WDT_OFF > Fuses _HS_OSC What speed crystal or resonator are you using? If it's 4MHz, use XT_OSC mode. {Quote hidden}>TEMP_B equ 078h ;temporary register > > org 0000h > >START > >INIT_PORTS > bsf RP0 ;point to bank 1 > bcf RP1 ; > movlw 10110011b ;set port c to 7->Rx, 6->Tx, 5->Dim, 4->Bright > movwf TRISC ;3->test out, 2->PWM, 1-> Zero, 0->Hold/Cont > movlw 00h ;load 0 into W > movwf SSPCON2 ;then into Sync Ser Port Cont 2 > movwf PIE1 > movwf PIE2 > bcf RP0 ;point to bank 0 > movlw 00h ;load 0 into W > movwf PIR1 > movwf PIR2 > movwf SSPCON ;then into Sync Ser Port Control >MAIN > movf PORTC, W ;read port C into W > movwf TEMP_B ;and into TEMP_B > andlw 00110011b ;mask off key bits > xorlw 00110011b ;any bits low? > btfsc Z ;if key pressed then skip > goto MAIN ;else jump > btfss TEMP_B,0 ;if Hold/Cont not set then jump > goto SCAN_H:C ;else jump IIRC, you can't have a colon in the middle of a label. {Quote hidden}> btfss TEMP_B,1 ;if Zero not set then jump > goto SCAN_ZERO ;else jump > btfss TEMP_B,4 ;if Brighten not set then jump > goto SCAN_BRIGHT ;else jump > btfss TEMP_B,5 ;if Dim not set then jump > goto SCAN_DIM ;else jump > goto MAIN >SCAN_H:C > bsf Portc,3 ;port C bit 0 low > bcf portc,3 ;so pulse bit 3 once > goto MAIN > >SCAN_ZERO > bsf Portc,3 ;port C bit 1 low > bcf portc,3 ;so pulse bit 3 twice > bsf Portc,3 bcf portc,3 > goto MAIN > >SCAN_BRIGHT > bsf Portc,3 ;port C bit 4 low > bcf portc,3 ;so pulse bit 3 three times > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > goto MAIN > >SCAN_DIM > bsf Portc,3 ;port C bit 5 low > bcf portc,3 ;so pulse bit 3 four times > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > goto MAIN > > end -- 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

"David V. Fansler" wrote: > > Dear PicList - I sent this email out yesterday asking why, or what I am > doing that would cause port c bit 5 to be pulled low internally to the chip. > The ensuing discussion has branched off to my use of using bcf, bsf to > toggle a bit on and off in order to get a feel for what the PIC was seeing - > this may or may not be proper code - it was just there for test purposes. > As to why bit 5 is hung low - not an educated - or even uneducated guess. > As I told my wife - I feel sort of like a guy who jumps out of an airplane - > his chute does not open and he radios for help. The people on the ground > get into a long winded discussion about what kind of handle he has on his > rip cord and why it should be something else - never addressing the real > problem. Sorry if I sound aggravated - I guess I was really hoping someone > had the answer as to why bit 5 is being held low instead of seeing > discussion on my use of bcf, bsf. > > Thanks to all, > David That sounds about right for a helpful list :-) You haven't initialised any of PORTA B D or E. These pins are inputs, and could be floating. This can cause all sorts of code problems. If the pins are unconnected, set them all to outputs and see if that changes anything. -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam@spam@bubblesoftonline.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> Dear PicList - I sent this email out yesterday asking why, or what I am > doing that would cause port c bit 5 to be pulled low internally to the chip. > The ensuing discussion has branched off to my use of using bcf, bsf to > toggle a bit on and off in order to get a feel for what the PIC was seeing - > this may or may not be proper code - it was just there for test purposes. > As to why bit 5 is hung low - not an educated - or even uneducated guess. > As I told my wife - I feel sort of like a guy who jumps out of an airplane - > his chute does not open and he radios for help. The people on the ground > get into a long winded discussion about what kind of handle he has on his > rip cord and why it should be something else - never addressing the real > problem. Sorry if I sound aggravated - I guess I was really hoping someone > had the answer as to why bit 5 is being held low instead of seeing > discussion on my use of bcf, bsf. Sounds like you got everything you paid for. I can't speak for others, but I didn't answer because your message was long and it looked like it would take more time than I wanted to devote to figuring it out. Nothing personal, but I do have real paying customers to take care of. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

HS mode, 20 Mhz David V. Fansler S/V Annabelle .....DFanslerKILLspam.....MindSpring.com http://www.dv-fansler.com -----Original Message----- From: pic microcontroller discussion list [EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU] On Behalf Of David Duffy Sent: Thursday, April 04, 2002 12:02 AM To: PICLISTspam_OUTMITVMA.MIT.EDU Subject: Re: [PIC]:16F873 PortC bit 5 revisited - the death of! At 10:59 PM 03/04/2002 -0500, you wrote: >Dear PicList - I sent this email out yesterday asking why, or what I am >doing that would cause port c bit 5 to be pulled low internally to the chip. >The ensuing discussion has branched off to my use of using bcf, bsf to >toggle a bit on and off in order to get a feel for what the PIC was seeing - >this may or may not be proper code - it was just there for test purposes. >As to why bit 5 is hung low - not an educated - or even uneducated guess. >As I told my wife - I feel sort of like a guy who jumps out of an airplane - {Quote hidden}>his chute does not open and he radios for help. The people on the ground >get into a long winded discussion about what kind of handle he has on his >rip cord and why it should be something else - never addressing the real >problem. Sorry if I sound aggravated - I guess I was really hoping someone >had the answer as to why bit 5 is being held low instead of seeing >discussion on my use of bcf, bsf. > >Thanks to all, >David > >Since my last post, I have simplified my code to almost nothing to try to >find out why my 16F873 wants to pull port c bit 5 low - the code is below. >In this case I set port c up then input port C, check to see if bits 0,1,4 >or 5 are low (they are pulled up to 5v by a 220 ohm resistor - pulling them >down is by a momentary push button switch). If one of the inputs is low the {Quote hidden}>code determines which one and jumps to code that then pulses port c bit 3 >either 1, 2, 3 or 4 times to indicate which button is pressed. I then can >observe the output bit via my oscilloscope. When the code runs in my >emulator all is well. But when I burn a 16F873 and place it in the circuit >the output shows 4 pulses without a button being pushed - sure enough bit 5 >is low on the oscope. Pull the 16f873 from the circuit and the pin goes >high. Something internal to the 16f873 is causing port c bit 5 to be low >(over riding the 220 ohm resistor). The only peripheral I can find on the >16f873 that shares port c bit 5 is the Sync Serial Port, but I feel that I >have disabled it. > >If anyone has any hints, I sure would be happy to hear them! >Thanks, >David > > > include 'c:\ptools\16f873.inc' > Fuses _CP_OFF > Fuses _DEBUG_OFF > Fuses _WRT_ENABLE_ON > Fuses _CPD_OFF > Fuses _LVP_OFF > Fuses _BODEN_OFF > Fuses _PWRTE_ON > Fuses _WDT_OFF > Fuses _HS_OSC What speed crystal or resonator are you using? If it's 4MHz, use XT_OSC mode. {Quote hidden}>TEMP_B equ 078h ;temporary register > > org 0000h > >START > >INIT_PORTS > bsf RP0 ;point to bank 1 > bcf RP1 ; > movlw 10110011b ;set port c to 7->Rx, 6->Tx, 5->Dim, 4->Bright > movwf TRISC ;3->test out, 2->PWM, 1-> Zero, 0->Hold/Cont {Quote hidden}> movlw 00h ;load 0 into W > movwf SSPCON2 ;then into Sync Ser Port Cont 2 > movwf PIE1 > movwf PIE2 > bcf RP0 ;point to bank 0 > movlw 00h ;load 0 into W > movwf PIR1 > movwf PIR2 > movwf SSPCON ;then into Sync Ser Port Control >MAIN > movf PORTC, W ;read port C into W > movwf TEMP_B ;and into TEMP_B > andlw 00110011b ;mask off key bits > xorlw 00110011b ;any bits low? > btfsc Z ;if key pressed then skip > goto MAIN ;else jump > btfss TEMP_B,0 ;if Hold/Cont not set then jump > goto SCAN_H:C ;else jump IIRC, you can't have a colon in the middle of a label. {Quote hidden}> btfss TEMP_B,1 ;if Zero not set then jump > goto SCAN_ZERO ;else jump > btfss TEMP_B,4 ;if Brighten not set then jump > goto SCAN_BRIGHT ;else jump > btfss TEMP_B,5 ;if Dim not set then jump > goto SCAN_DIM ;else jump > goto MAIN >SCAN_H:C > bsf Portc,3 ;port C bit 0 low > bcf portc,3 ;so pulse bit 3 once > goto MAIN > >SCAN_ZERO > bsf Portc,3 ;port C bit 1 low > bcf portc,3 ;so pulse bit 3 twice > bsf Portc,3 bcf portc,3 > goto MAIN > >SCAN_BRIGHT > bsf Portc,3 ;port C bit 4 low > bcf portc,3 ;so pulse bit 3 three times > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > goto MAIN > >SCAN_DIM > bsf Portc,3 ;port C bit 5 low > bcf portc,3 ;so pulse bit 3 four times > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > bsf Portc,3 > bcf portc,3 > goto MAIN > > end -- 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 PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>...I feel sort of like a guy who jumps out of an airplane - >his chute does not open and he radios for help. The people on the ground >get into a long winded discussion about what kind of handle he has on his >rip cord and why it should be something else - never addressing the real >problem. Hmmm, I guess you aren't aware of where Engineers get their reputation... Truth is, I was watching as the discussion ranged around as you described, yet I was waiting for some reply from you to say what you might have tried so far. Also I may have erred in assuming you'd had a lot of experience with PICs; after all, you were on this list back when I joined it. So I didn't even mention the bcf thing. Others did. It got too detailed. In short, there is a syndrome (here I carefully avoid the bug/feature discussion) wherein you can shoot yourself in the foot. You may be the one who is setting that pin low, and not know why. It is directly connected to the bcf PORT instruction. My suggestions were designed to get you past all the "maybe you have a bad chip" type questions you would inevitably be receiving. The question remains: Can you get that pin to float, in your circuit, under ANY circumstances? Strip the code to setup the port all as all inputs, and then go into a loop. If that works, put back in the some-in-and-some-outs setting for TRIS. Keep adding stuff until it breaks again. HTH...Barry -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

David V. Fansler S/V Annabelle @spam@DFanslerKILLspamMindSpring.com http://www.dv-fansler.com -----Original Message----- From: pic microcontroller discussion list [KILLspamPICLISTKILLspamMITVMA.MIT.EDU] On Behalf Of Olin Lathrop Sent: Thursday, April 04, 2002 8:08 AM To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU Subject: Re: [PIC]:16F873 PortC bit 5 revisited - the death of! > Dear PicList - I sent this email out yesterday asking why, or what I am > doing that would cause port c bit 5 to be pulled low internally to the chip. > The ensuing discussion has branched off to my use of using bcf, bsf to > toggle a bit on and off in order to get a feel for what the PIC was seeing - > this may or may not be proper code - it was just there for test purposes. > As to why bit 5 is hung low - not an educated - or even uneducated guess. > As I told my wife - I feel sort of like a guy who jumps out of an airplane - > his chute does not open and he radios for help. The people on the ground > get into a long winded discussion about what kind of handle he has on his > rip cord and why it should be something else - never addressing the real > problem. Sorry if I sound aggravated - I guess I was really hoping someone > had the answer as to why bit 5 is being held low instead of seeing > discussion on my use of bcf, bsf. Sounds like you got everything you paid for. I can't speak for others, but I didn't answer because your message was long and it looked like it would take more time than I wanted to devote to figuring it out. Nothing personal, but I do have real paying customers to take care of. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. To: Olin "Deathdrop" My husband sent the request for help. He is at work now so I would like to respond as I would, not he. It appears that money is more important to you than helping another. I hope there never comes a time that you need help (if you do not you will be the first) and the response you receive is "I do not have time for you, money is more important". We reap what we sew. You probably do not know the answer anyway. Pitiful cover-up. Madlyn -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> To: Olin "Deathdrop" > > My husband sent the request for help. He is at work now so I would like to > respond as I would, not he. It appears that money is more important to you > than helping another. I hope there never comes a time that you need help > (if you do not you will be the first) and the response you receive is "I do > not have time for you, money is more important". We reap what we sew. Look, Madlyn spamBeGoneDFanslerspamBeGoneMINDSPRING.COM, you are way out of line. I can see you will find this hard to believe, but I am not your personal consultant. I and everyone else on this lists who choses to answer questions does it on their own time. I don't owe you anything, including an explanation of why I chose not to respond. Nobody has the time to respond to all questions, so we all have to pick which questions to answer. Some factors that enter into this decision are: 1 - Is the question easy and quick to read? 2 - Do I know the answer (assuming the question was easy and quick enough to read)? If not, how long might it take to find the answer? 3 - Has the poster tried reasonable ways to find the answer himself, or is he expecting me to do all the work for him? 4 - Has some care been taken in asking the question? People who write like a mess usually think like a mess. Answering a question to someone like that is a waste of time. In your case the question just seemed to long and I had urgent things to do. This was not meant as an insult, only a reflection of the fact that my time is finite and there isn't enough of it to do all things I and others would like me to do. I even took the trouble of explaining this. > You probably do not know the answer anyway. Pitiful cover-up. > > Madlyn As I already said, I don't even know the question since I didn't have time to read it. What is pitiful is insulting someone because they didn't donate their time to just you personally. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.