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ADDC in C51

Jorge Cases


What is the most efficient way of assembly instruction ADDC in C51?

Is the following allowed

int add_high,carry,low_poti;

TL0=0x69+low_poti;
TH0=0xF8+add_high+CY;

Or should I do the following?
int add_high,carry,low_poti;

TL0=0x69+low_poti;
if (CY==1)
carry=1;
else
carry=0;
TH0=0xF8+add_high+carry;

  • 0

    Why don't you write C code rather than trying to write assembler code in C. Then, you won't have to worry about the carry bit and such things. For example:

    unsigned int new_timer_reload;
unsigned int low_poti;

new_timer_reload = 0xF869 + low_poti;

TL0 = new_timer_reload;
TH0 = new_timer_reload >> 8;

    You may want to stop the timer before reloading it and restart it afterwards.

    Jon

  • 0

    Jon is right - if you want to do assembler programming, do it in assembler!

    It is not safe to assume that the Carry flag will contain the "correct" value between 'C' statements (it might happen to work in some specific case, but it ain't necessarily so!)

    'C' provides you with multi-byte data types specifically so that you don't have to manually mess about with the carry flag!