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