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How to use JNC or JC from C

C S

I want to generate very efficient code using the carry-bit from C-code, and the instructions JNC or JC.

...
sbit PinBit= P0^0;              //port-IO bit
...
CY=PinBit;              //generates MOV C,PinBit
...
if(CY)
{
        //do something
}
IfNotCY:
...

The if(CY) instructiuons generates JNB CY,IfNotCY

How can i get it to use the more efficient JNC IfNotCY?

Analogously, if(!CY) should generate JC {label}.

Parents
  • 0 in reply to C S

    "i was just trying to stick with C, to make readabillity and debugging easier."

    Exactly - that's the (potential) programmer productivity gain from using a HLL.

    But, when absolute timing control is critical, you have nothing to trade - you must stick with assembler.

    But be sure to be extra careful in the documentation of your assembler - well documented, well structured assembler need not be hard to debug or maintain!

Reply
  • 0 in reply to C S

    "i was just trying to stick with C, to make readabillity and debugging easier."

    Exactly - that's the (potential) programmer productivity gain from using a HLL.

    But, when absolute timing control is critical, you have nothing to trade - you must stick with assembler.

    But be sure to be extra careful in the documentation of your assembler - well documented, well structured assembler need not be hard to debug or maintain!

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