:?

Hi i´m new here, I´m from Bogotá, Colombia and I have a question.
i don´t know wether the issue i´m having programming a PIC 16f877 is very simple or not, however I do know it´s driving me crazy.


Well, I have programmed this PIC (just assembly) to interface with an LCD and also some pushbuttons. Right now everything works, however when i try to add even a little instruction, the microcontroller goes crazy.

I used the degug option in MPLAB and effectively there is problem, when the microcontroller goes into a certain Call subroutine it suddenly jumps to another call routine that is right before that one. I have checked all my labels and no problem there, But it is when I add even the slighttest code in some other area that this problem occurs. I have also checked the pages numbers for both program and data memory. For program memory I´m below the 2000 words so I should be on page 0.
Also the pages for the data memory should be okay since the code works fine, up until i try to add any instruction.

I have also checked with the debugger the stack making sure that I don´t call more than 8 subroutines at the same time (I believe the stack is eight levels deep from the data sheet).

I would greatly appreciate if someone could help me out here. I have to say that this is the first time I´m programming with a PIC and I don´t know many things. On the other hand if the information provided here is not enough I would send code or explain more the problem.

Again thanks, if someone has a suggestion as to why this might be happening.

Ivan

If you want help,posting your code would be your best bet.

As I mentioned, whenever i try to put code anywhere, this program stops working. Also to acces RAM memory locations at 20h to 7Fh on page 0, I have to be on page1 which i think is wrong, but then again i´m probably missing something.

The code is in zip format

Hey i don't have the emulator on this computer, so i'm not gonna even try to read all that code (looks like a hudge project) only remind you that the PC is only 8bit, so u need to set PCALH
(the higher bits)
From what your saying this sounds like the problem.

just thought to glance over your code by eye.

Clearlcd is called accross a boundary, and i can't see PCLATH been set properly!!

Hi animus!!!
Thanks for looking over that huge code. You know i really don´t know wha t you mean by
"Clearlcd is called accross a boundary, and i can't see PCLATH been set properly!¨"
But i do know that that might be were the problem is because, suddenly that is the subroutine that keeps coming up. In other words the LCD keeps clearing up after I add any code. I did discover some errors in page numbers that fixed some other bugs but the Cleralcd problem is still there.

Could you explain to me very quick what is a boundary and how do I set PCLATH properly???
At the moment i´m reading more of the data sheet, so that i´m trying to understand about the PC. The routines that use for the text strings fo the LCD, are from the internet and i don´t even know how they work

Again thanks for you help, which I greatly appreciate.