Connect with us

What's wrong?

Discussion in 'Electronic Basics' started by [email protected], Feb 14, 2004.

Scroll to continue with content
  1. Guest

    Hi all,
    I'm really losing my mind now, been fighting with this for 8 days
    now, I give up. I hope you can tell me what's wrong in my setup. :(

    I self made a PIC18F8720 development board, and it seems to work,
    because I can program the chip with no problems.

    I'm using 100 nF SMD capacitors near every Vdd (including AVdd),
    and an integrated clock oscillator. It's a 24 MHz CMOS part by

    I wrote a simple test program which is supposed to set all ports
    to output (via the TRISx registers), and then put all of them to
    the "HIGH" logic level (via the PORTx registers).

    This is my code, as shown by IC-Prog:
    0000: D00F 0000 0000 0000 0000 0000 0000 0000
    0008: 0000 0000 0000 0000 0000 0000 0000 0000
    0010: 0000 0E00 6E92 6E93 6E94 6E95 6E96 6E97
    0018: 6E98 6E99 6E9A 0000 0000 0000 0000 0000
    0020: 0EFF 6E80 6E81 6E82 6E83 6E84 6E85 6E86
    0028: 6E87 6E88 0000 0000 0000 0000 0000 0000
    0030: D7DE 0000 0000 0000 0000 0000 0000 0000

    And this is the configuration:
    Config1 = 2500
    Config2 = 000F
    Config3 = 0080
    Config4 = 0081
    Config5 = C0FF
    Config6 = E0FF
    Config7 = 40FF
    ID Value = 0123456789ABCDEF

    Is there anything wrong in my machine code (for this quick test
    I don't want to nor I think I need to install MP-Lab.. I tried
    it and hated it, I will write my own source level debugger and
    assembler and release it to the PD after I'm finished).

    Is the reset vector ok? It's supposed to be a BRA to 0010, where
    it will meet a NOP (no reason in particular) and then the value
    00 will be moved to W, which in turn will be moved to all the
    TRISx registers. Then W will be loaded with FF, which will be
    copied to all the PORTx registers. Finally (through some NOPs,
    again, just to leave some space for inserting other code for
    experiments) there's supposed to be a final BRA back to 0010.
    Addresses don't represent bytes, but instruction words.

    I know it's tedious to go through machine code.. but if you're
    kind enough, and if the code or the configuration is wrong, please,
    can you point me to the errors?

    Or, in alternative, could some kind soul post a small .HEX file
    with a demo program that just turns some port pins ON and some
    others OFF, just to see if my problem lies in my hardware or in
    my code?

    I hope to get your valuable help.. I really don't know what to
    experiment else.

    Kindest regards,
    Mike Forrest
  2. Willem

    Willem Guest

    No idea about the PIC thing but your use of the e-mail
    adres is wrong.... The domain actually exists and e-mail address harversters
    don't check for this kind of problem. Better use something like

  3. vic

    vic Guest

    If I was programming in raw machine code, i'd be losing my mind too ...

    You must have a really high opinion of us if you expect us to read and
    program raw machine code directly.

    The instruction at 0x00 is a bra 0x20, not bra 0x10. I didn't bother to
    check the other ones (seem ok) but it should be the problem since TRISx
    registers reset values are 0xFF.
    Don't reinvent the wheel ... you'll lose lots of time doing this. MPLAB
    is quite a good tool, it includes several features like a simulator
    which are quite useful.
  4. Yes, correct. (D00F = BRA 0x00F)
    Correct (0000)
    Correct (0E00 = MOVLW 0x00)
    Correct (6E92...6E9A)
    Actually, I'm looking at the PIC18C Reference Manual and it only lists
    0x92 to 0x96 as TRISx registers, but I'll assume your particular
    processor implements 0x97 to 0x9A. Those addresses are otherwise
    unused, so there's no down side. :)
    Correct (0EFF = MOVLW 0xFF)

    Again, the general manual only shows PORTA thru PORTE (at 0x80 to
    0x84) but I'll make a parallel assumption with the parallel lack of
    down side.
    Yes (D7DE = BRA -0x021)
    I haven't checked your configuration yet, but the code looks fine.

  5. Sam B.

    Sam B. Guest

    wrote in message
    I'm not a PIC expert, but I'll offer my two cents worth...
    I suppose that you can also read back what you wrote to the chip,
    Some chips will have some sort of extra global port enable that needs
    to be set before the port pins can be used at all.
    Don't give up so easily... I built my own eval board for the TI
    '5402 DSP chip some time ago. I remember that it took me 1-2 weeks
    to figure out how to properly use the serial port, as a beginning
    step. In the end, it turned out to be a piddling problem of the CPU
    just writing the most and least significant words in inverted (wrong)
    fashion to the serial port TX registers. Seems the documentation
    wasn't immediately obvious in that regard. That first problem is
    always the hardest to deal with, but it gets easier after that.

    Sam B.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day