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Bringing up a PXA250 board

Discussion in 'Embedded' started by gordon, Jul 10, 2003.

  1. gordon

    gordon Guest

    I have built a PXA250 board around the form factor reference design
    from Intel. So far, I have been able to (1) get a JTAG connection
    using OCDemon and Wiggler, and (2) flash (and verify the flash) a
    u-boot boot-loader using openwince and the Wiggler.

    I hate to say I'm stuck, but I have not been able to get the PXA250 to
    do more than 1 step out of Reset-- either from JTAG-reset or
    hard-reset-- which is a Branch from 0x00000000 to 0x00000060. When I
    "Reset and Go" from OCDemon I get the error "run_target_from_pc:
    target bus error (20:11)" which I cannot interpret. This is before
    initializing anything-- i.e. SDRAM, etc.

    I would appreciate any clues or ideas, and I have attached some
    (possibly) relevant information.

    Gordon

    A. Board info
    PXA250 Stepping B1 400MHz
    64MB 100MHz SDRAM
    4MB Strataflash
    SDCard
    Power supply

    B. OCDemon data after hard-reset
    PC: 00000000 SP: FFFFFFFF LINK: 00000054 CPSR: 180000D3
    B 060H ! Reset

    C. OCDemon data after "Step"
    PC: 00000060 SP: FFFFFFFF LINK: 00000054 CPSR: 180000D3
    MRS R0, CPSR

    D. OCDemon data after "Go"
    PC: 00000060 SP: FFFFFFFF LINK: 00000054 CPSR: 180000D3
    MRS R0, CPSR
    "run_target_from_pc:target bus error (20:11)" appears in the bottom
    left panel.


    and that's all I have been able to do...
    again, thanks in advance.

    gordon
     
    gordon, Jul 10, 2003
    #1
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  2. gordon

    Gary Kato Guest

    Bus Error means the CPU is trying to access a memory location but nothing is
    responding. From what you're saying, there's a branch to $60 at location 0.
    What instruction is at location $60? I'd think that might give a clue.
     
    Gary Kato, Jul 10, 2003
    #2
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  3. gordon

    gordon Guest

    Thanks, Gary.

    Address $60 is in flash, but seems to be readable because it OCDemon
    de-assembles it correctly. What puzzles me is that the instruction
    which fails is the "MRS R0,CPSR" which, as far as I know, involves
    nothing off-chip. Have I misunderstood this?

    In the meantime, I have been able to load some other innocuous
    instructions (not involving the CPSR) into $8000 (also still in flash)
    that are able to execute in Debug mode; i.e. I am able to step
    through them.

    Do you know anything about CPSR anomolies?

    I appreciate your help.

    Gordon
     
    gordon, Jul 11, 2003
    #3
  4. gordon

    Gary Kato Guest

    It might not be the instruction at $60 that is giving the problem, but possibly
    the instruction after that. As you point out, OCDemon seems to fetch it just
    fine. Instead of a GO, do another step and see what the registers are. I think
    the PC should be $0C if it's an instruction prefetch problem, or $10 is it's a
    data fetch problem. The low 5 bits of the CPSR should be %10111 which means the
    CPU is in Abort mode. The LINK register should have the address of the aborted
    instruction +4 for prefetch or +8 for data fetch.
     
    Gary Kato, Jul 11, 2003
    #4
  5. gordon

    Gary Kato Guest

    Hmm. The exception stuff I replied with was from an ARM6 manual I had sitting
    around. Looks like things might be different on the PXA so consult the User
    Manual on what happens on an Exception.
     
    Gary Kato, Jul 11, 2003
    #5
  6. gordon

    gordon Guest

    Will do.

    I have experimented with a bunch of different instructions, and the
    common fail-point is reading instruction from flash with address <=
    0x0800. Everything else seems fine [so far...]

    Thanks,

    Gordon
     
    gordon, Jul 11, 2003
    #6
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