Post by thread:[PIC]: On-Chip Debugging

Thanks to all who have pointed at Microchip's DS51242A, "PIC16F87X Debugger Control". I've studied that so hard for the last week I can almost recite it from memory, and still have some fundamental questions on how this works. Here's the most mind-boggling: The document states on page 10 describes how the debugger code gets control: "As the processor vectors to 0x2004, the CPU will fetch and execute the instruction at this address. Therefore, address 2004 must be programmed with a GOTO opcode, where opcode is pointing to the beginning address of the debug code." I really can't wrap my head around this statement because it would seem that the current contents of PCLATH would determine which page of memory the GOTO statement would transfer to. Is there some special form of GOTO that must be used? This is one of several questions pondered by Myke Predko, Bob Ammerman, Tony Nixon, Dmitry Kiryashov, Olin Lathrop and Alejandro Lavarello back in May of this year. If answered, I can't find it in the archives... Any clues? Thanks, Steve -- 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

I think that the conclusion that we came to is that location 2004 should not be programmed with a GOTO, but with the full actual address of the ICD handler code. I forget they basis on which we came to this conclusion however. Perhaps wishful thinking? Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) {Original Message removed}

Bob Ammerman wrote: > > I think that the conclusion that we came to is that location 2004 should not > be programmed with a GOTO, but with the full actual address of the ICD > handler code. I forget they basis on which we came to this conclusion > however. Perhaps wishful thinking? Maybe(???) the data at 2004h is placed directly into the PC like a return address off the stack. You don't need the PCLTAH then. -- Best regards Tony mICros http://www.bubblesoftonline.com spam_OUTsalesTakeThisOuTbubblesoftonline.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

----- Original Message ----- From: "Tony Nixon" <.....Tony.NixonKILLspam@spam@ENG.MONASH.EDU.AU> To: <PICLISTKILLspamMITVMA.MIT.EDU> Sent: Wednesday, July 18, 2001 4:25 PM Subject: Re: [PIC]: On-Chip Debugging > Bob Ammerman wrote: > > > > I think that the conclusion that we came to is that location 2004 should not {Quote hidden}> > be programmed with a GOTO, but with the full actual address of the ICD > > handler code. I forget they basis on which we came to this conclusion > > however. Perhaps wishful thinking? > > Maybe(???) the data at 2004h is placed directly into the PC like a > return address off the stack. You don't need the PCLTAH then. > > > -- > Best regards > > Tony Yeah, that's what I was saying. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

Thanks to Bob and Tony for the replies. I'll stay after this until the pain becomes too great and will share whatever new info develops. Regards, Steve -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body