Electronic – What’s the most effective way to save/restore a PIC status bit

assemblypic

I want to save/restore the PIC's carry bit. I'm using the 16F628A.

SAVE_CARRY
    btfss STATUS, 0
    goto CARRY_OFF 

CARRY_ON
    bsf carry, 0
    return

CARRY_OFF
   bcf carry, 0
   return

RESTORE_CARRY
   btfss carry, 0
   goto RESTORE_CARRY_OFF

RESTORE_CARRY_ON
   bsf STATUS, 0
   return

RESTORE_CARRY_OFF
   bcf STATUS, 0
   return

There must be a better way. Is there?

Best Answer

One way that you can do:

SAVE_CARRY:
    bsf    carry, 0
    btfss  status, c
    bcf    carry, 0
    return

RESTORE_CARRY
    bsf    status, c
    btfss  carry, 0
    bcf    status, c
    return

If you need to save the registers "W" and "Status", before execute an interrupt code, there is another way:

Save_Context:
    movwf w_temp
    swapf status,w
    movwf status_temp
    ;Your interrupt code here. 

Restore_Context:
    swapf status_temp,w
    movwf status
    swapf w_temp,f
    swapf w_temp,w
    retfie

Related Solutions

Electronic – pass a bit register as a function argument in Hi-Tech C compiler for PIC16

Maybe this would work, but it is not standard C:

void setBitHigh( bit *b ){
   b = 1;
}
setBitHigh( & RB3 );

If not, then there is no direct way to do what you want. You could of course return the value from the function and then assign it:

RB3 = newBitValue();

or you could pass the function both the byte address and the offset, and leave it to the function to do the dirty work:

void setBitHigh( unsigned char *a, bit_offset b ){
   *a |= ( 1 << b );
}
setBitHigh( & PORTB, 3 );

Electronic – Save energy with PIC project

Yes, interrupts and sleep mode are the best way of doing this. There is a list of ways to minimise PIC energy consumption in an app note: http://ww1.microchip.com/downloads/en/devicedoc/01146b_chapter%202.pdf

Best Answer

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Electronic – pass a bit register as a function argument in Hi-Tech C compiler for PIC16

Electronic – Save energy with PIC project

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