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csyntaxxc8

C/XC8 Syntax: Can invert and AND operation be used in the same statement?

I am writing c code in xc8 compiler for PIC micro-controller. This code will control a fan's(motor) on/off and speed using CCP module.

To turn on/off the CCP module and consequently the fan, I am toggling the CCP1CON bits like so

ccp1conValue = CCP1CON;
ccp1conValue = ~ccp1conValue & 0x0F;
ccp1conValue = CCP1CON;

My concern is that is this syntax correct and acceptable in XC8? Can I use invert and AND operation in the same statement or I need to do them separately? Or is there a better way to do it altogether?

Solution

  • It's valid C syntax, and any slightly compliant compiler should handle it with grace. While people often push what is reasonable to do in a single line of C code, I would personally judge what you've done to be perfectly acceptable.

    One thing to watch out for whenever you combine multiple operations is operator precedence.

    Your statement:

    ~ccp1conValue & 0x0F

    is equivalent to:

    (~ccp1conValue) & 0x0F

    This is likely what you were trying to do, but it's good to keep in mind.

    Also, that last line:

    ccp1conValue = CCP1CON;

    should probably be:

    CCP1CON = ccp1conValue;

    instead.

    Depending on if you need to keep the value, you may be able to replace those three lines with:

    CCP1CON = ~CCP1CON & 0x0F;