Dear Mr. Ian I am using 16f874 and facing problem, program did't executing randomly. I am using HS oscillator (20mhz) and high voltage programming mode. and disable all other configuration bits. kashif ali Ian Holbrough wrote: > I need to preface this with the statement that I am a newbie and I have I > have not had this confirmed by the older and wiser members of the group > (anyone care to offer?). I have seen similar problems. I think I have > tracked this down to the following... > > You must be very careful when using Port B on the 87x, given its use in > programming the IC. I found that the IC would seem to get into a nasty > state if you set RB3 to an output when the LVP bit in the Status register > was set. (i.e. you tried to drive the output as well as using it as > programming input). Now given the other notes on the RB3 I can see how a > catch 22 situation could arise. > > In the PIC FAQ it states that to use LVP you must leave RB3 low initially > and only raise it once MCLR is at Vdd. At this point of course the CPU is > in run mode and your code will try to set RB3 to an output presumably > preventing or clashing with its use as a programming input. If you try to > prevent the chip getting into run mode you must raise RB3 to Vdd at the same > time as MCLR which runs into the whole RB3 bug thing. As an aside I > typically also saw a siginificant current drawn and warming of my 877 when > it was acting up do you see this too? > > So assuming this limbo state exists, is it possible to get the chip out? > Well I have not yet tried high voltage programming the IC with RB3 held low. > I will be trying that next. > > Ian > > ----- Original Message ----- > From: "David A. Gianna, MS, CCSE, ACE/ADM" > To: > Sent: Thursday, July 19, 2001 9:32 PM > Subject: Re: Dead 16F876 > > > I have had the same problem - mind you, the PIC 16f876 is new to me -- > > > > I wrote a trivial program to blink an LED (the equivalent of print hello), > and > > an even more trivial program to set all outputs on every port high. > > My logic probe does not show either high or low, so it appears to be > tri-stated. > > I am using a single 8Mhz 3-pin resonator. > > > > The .hex file was compiled without errors on MPLAB, and loaded to the chip > with > > the 2bit programmer. > > I can NOT verify if the program was loaded correctly, since I do not have > a > > 4401A transistor, only a 4401. > > The level of frustration is beyond words. ;( > > > > all I know is that 2Bit recognizes that the chip is there, and apparently > > handshakes with it. > > > > How do you run the chip? I disconnected the programming voltage (I don't > recall > > verbatim off-hand, but this did not work). > > trying the -e option in 2Bit revealed that the chip is already erased. > > > > Is this chip bad? BTW, I have two more, new in static-free wrap. > > > > > > > > Dave Gianna, MS, CCSE, CCSI, ACE/ADM > > Technical Sales Engineer > > Security Technologies Group > > (914) 829-7351 > > Westcon, Inc. > > 520 White Plains Road > > Tarrytown, NY 10591 > > > > ==================================================== > > "Sing bird of prey, Beauty begins at the foot of you > > Do you believe the manner? > > Cold stainless nail, Torn through the distance of man > > As they regard the summit ..." > > -- Jon Anderson/Yes > > ==================================================== > > > > > > > > > > |--------+-----------------------> > > | | "Dipperstein,| > > | | Michael" | > > | | > | | RIS.COM> | > > | | | > > | | 07/19/01 | > > | | 04:20 PM | > > | | Please | > > | | respond to | > > | | pic | > > | | microcontroll| > > | | er discussion| > > | | list | > > | | | > > |--------+-----------------------> > > > >--------------------------------------------------------------------------- > -| > > | > | > > | To: PICLIST@MITVMA.MIT.EDU > | > > | cc: (bcc: David Gianna/Westchester/Westcon/US/WestconGroup) > | > > | Subject: Re: Dead 16F877? > | > > > >--------------------------------------------------------------------------- > -| > > > > > > > > > > > > Does the chip consume any current? > > > > Does the oscillator oscillate? > > > > -Mike > > > > -----Original Message----- > > From: Michael A. Powers [mailto:mapowers@email.com] > > Sent: Thursday, July 19, 2001 1:07 PM > > To: PICLIST@mitvma.mit.edu > > Subject: Dead 16F877? > > > > > > Hello, > > > > I've been having some problems with a 16F877 I have, it simply doesn't > work. > > The program I have it running is trivial for diagnostic purposes, just > turn on a > > LED on RB5 with a pull-up resistor. My tests have shown that although RB5 > is > > low, it must be tristated because it cannot sink any current. RB5 (or any > other > > I/O pin for that matter) is incapable of going high as well. I have not be > able > > to ascertain much more than that about the problem, because the chip > behaves the > > same whether power is applied or not! I have connected 11 and 32 to +5 > and 12 > > and 31 to GND, but surprisingly the presence or absence of these > connections > > does not seem to have any effect on the output, which makes me suspicious > of > > the fact that the chip is dead. It is brand new, although I have not used > it > > before. Does anyone have any suggestions? > > > > Thanks, > > -Mike > > > > P.S. I am not sure if the caps on the crystal meet the spec exactly, but > it > > works fine on a 16F84. > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > > > > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads