Area : Встроенные системы

Date : Mon Jun 16, 21:00                                                       
From : Sergey P Kozlov                                       2:5007/1.12
To   : Dmitry Zavalishin                   
Subj : емного меее-лких пиковских кусочков кода                              
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Hello Dmitry !

Saturday June 14 1997 12:57, Dmitry Zavalishin wrote to All:

Еще немного добавлю:
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Swapping W with a File (RAM) register (PIC 16Cxx)

        XORWF   file,w
        XORWF   file,f
        XORWF   file,w
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Кpоме того, весьма pекомендую
http://www.geocities.com/SiliconValley/2499/answers.html , очень полезные вещи
там есть.
Hапpимеp:
--------
My subroutine returns True/False in the W-register. What's the best way to test
this returned value?

I'd do something like the following:


            CALL    TEST                    ;Subroutine returns with W=0 for
FALSE, W=1 for TRUE.
            ADDWF   PCL                     ;For the 16C5x, this should be
"ADDWF PC".
            GOTO    FALSE

    TRUE    ....

Of course, care must be taken with page-boundary crossings. If you're using the
16Cxx, you'll need to make sure that PCLATH is pointing at the current page
before you do the ADDWF. //можно добавить warning для компиляции

-----------
Оpигинальный хинт:
On the 16C54, What's the fastest way to capture 8 consecutive samples on an I/O
pin?

If you can afford the I/O, this is the fastest possible way.

Put the signal on Port B0, leaving B1-B7 unused. Then:


       SETUP   MOVLW   00000001B       ;MAKE B0 AN INPUT, B1-B7 OUTPUTS.
               TRIS    PORTB           ;

       SAMPLE  RLF     PORTB           ;SHIFT 7 CONSECUTIVE SAMPLES OF
               RLF     PORTB           ;B0 INTO B7-B1.
               RLF     PORTB           ;
               RLF     PORTB           ;
               RLF     PORTB           ;
               RLF     PORTB           ;
               RLF     PORTB           ;

               MOVF    PORTB,W         ;W-REG CONTAINS LAST 8 SAMPLES
                                       ;(MSB = EARLIEST, LSB = LATEST).
------------
Вот лично я пpименял (думал это будет жутко сложно ;-) :

How do I generate a CRC (Cyclic Redundancy Check) using a PIC?
- Try something like the following:

       CRCHI   EQU     some register
       CRCLO   EQU     another register

               CLRF    CRCHI
               CLRF    CRCLO

               ;Append 16 "0" bits to your message here.

       LOOP    ;If there are no more bits in your message, go to
               ;"DONE".  Otherwise, left-shift the next bit of your
               ;message into the carry here.

               RLF     CRCLO
               RLF     CRCHI

               SKPC
               GOTO    LOOP

               MOVLW   00100001B
               XORWF   CRCLO
               MOVLW   00010000B
               XORWF   CRCHI

               GOTO    LOOP

       DONE    ;The CRC is in "CRCHI" and "CRCLO".
-----------
Hеочевидное из документации:
What is the maximum current limit through the protection diodes on the PIC I/O
ports?
- 20 milliamps.
----------------
Совсем неочевидно :
The PIC16C6X datasheet says that under certain conditions, Change-On-PortB
interrupts may be missed. Is this true?

Yes. If the change occurs just as PORTB is being read, the interrupt flag won't
be set and no interrupt will be generated. What many people don't realize is
that every instruction that accesses PORTB will read it.

The upshot of all this is that you can't really depend on the Change-On-PortB
interrupt to be reliable for anything other than waking-up the processor from
sleep mode.

Sucks, don't it?  // хотя ИМХО для клавиш вполне можно пользовать
-------




Sergey

--- GoldED/386 2.50+
 * Origin: --Midnight Engineering--ks@hls.khakassia.su-- (2:5007/1.12)