Electronics Quick PIC questions

Discussion in 'Modding' started by ch424, 28 Jun 2005.

  1. ch424

    ch424 Design Warrior

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    Hi,
    I couldn't find this on google, so two quick questions:

    1. If you have 0x00 in a reg, then do
    decf reg,f
    (therefore reg = 0xFF) does the carry flag get set?

    2. If you have 0x00 in the working register and 0x00 in a reg, then you do
    subwf reg,f
    will the carry flag get set?

    I'm getting otherwise inexplicable behaviour from the MPLAB simulator and a 16F84.

    Thanks for any help

    ch424
     
    ch424, 28 Jun 2005
    #1
  2. SteveyG

    SteveyG Electromodder

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    1. No
    2. Yes
     
    SteveyG, 28 Jun 2005
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  3. TheAnimus

    TheAnimus Banned

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    all in the data sheets.
     
    TheAnimus, 28 Jun 2005
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  4. SteveyG

    SteveyG Electromodder

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    Indeed. If you're getting "inexplicable behaviour" you've mis-read or not read something ;)
     
    SteveyG, 28 Jun 2005
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  5. TheAnimus

    TheAnimus Banned

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    i wouldn't go that far, the sim does have some limitations (thou most seam documented... now) but its often someone does something silly (like let MCLR float) and can't figure out why their code isn't behaving properly.

    The art of PIC programming is reading the datasheets. Multipule monitors kick arse for this! (or a laptop or something to read the datasheets (product line + device datasheet).
     
    TheAnimus, 28 Jun 2005
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  6. SteveyG

    SteveyG Electromodder

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    Yeah, but he said the sim AND his PIC... :)

    A laser printer is also useful for those datasheets :)
     
    SteveyG, 28 Jun 2005
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  7. ConKbot of Doom

    ConKbot of Doom Minimodder

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    I wouldnt try one for the Mid-Range MCU Family Reference manual though :p

    Maybe sections, but not the whole thing.
     
    ConKbot of Doom, 28 Jun 2005
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  8. ch424

    ch424 Design Warrior

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    Ah, great thanks - I hadn't thought of checking the actual datasheet! QUOTE: "2: Yes" explains why I'm getting these problems! I'll have to re-write that bit of the program then!

    thanks again

    ch424
     
    ch424, 29 Jun 2005
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  9. ch424

    ch424 Design Warrior

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    ch424, 29 Jun 2005
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  10. SteveyG

    SteveyG Electromodder

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    It's just due to the way you subtract 2's compliment numbers.

    ConKbot.. I have the midrange manual, and 16 of the PIC datasheets for 10F, 12F, 16F and 18F series printed out. :p:)
     
    SteveyG, 29 Jun 2005
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  11. TheAnimus

    TheAnimus Banned

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    TheAnimus, 29 Jun 2005
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  12. ConKbot of Doom

    ConKbot of Doom Minimodder

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    Thats what I should have done while still in school... :duh:
     
    ConKbot of Doom, 29 Jun 2005
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  13. TheAnimus

    TheAnimus Banned

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    multipule monitors kick arse!
     
    TheAnimus, 2 Jul 2005
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