pl explain this to me (89s52 c code)

[lgeorge123]

i have the following code from somewhere and tried to transfer to pic18f452 so i have to understand the code first.
void WriteByte()
{
uchar k;
for(k=0;k<8;k++)
{
dat=dat<<1;
R1=CY;
R2=1;
CLK=0;
CLK=1;
}
}

I guess the code is transfer the 7th bit of dat to R1 until all of the dat is done , am I correct ????

 

[aProgrammer]

I think "CY" is the 89s52's carry flag,
so R1 receive all "dat" bits (from msb to lsb)

because whe can suppose
dat << 1 shift the msb bit to carry but this is absolutly not portable,
this a 89s52 or compiler trick

You need to examine the generated code
to see if this can work with the pic18F

 

[btbass]

You could achieve the same result using this code snippet.

uchar k;
uchar dat;


for(k = 0;  k < 8; k++) /* MSB first */
    {
    DATA_OUT = ((dat << k) & 0x80U) ? 1 : 0; 

    CLOCK = 0;
    CLOCK = 1;
    }