high voltage programming is always available no matter what you are doing with RB3 dld On Sat, 21 Jul 2001 06:56:17 +0100, 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