Need BINARY to BCD function

Hi,

Thanks for the HELP. No its not homework...I finished school long time ago :-) It was for communicating with a DALLAS RTC DS1337.

Is your code better than this one ? I mean will it run faster ?

Because I didn't use the MODULO 10, here is what I did:

char bin2BCD8(char cValue)
{
char cDig10=0;
char cDig1=0;
char cTemp;
cTemp=cValue; // Backup the value
do{
cTemp=cTemp-10;
if(cTemp<0)
{
break;
}
else
{
cDig10++;
}
}while(1);
cDig1=cValue-(cDig10*10);
cDig10=(cDig10<<4)|cDig1;
return cDig10;
}

Hi,

Thanks for the HELP. No its not homework...I finished school long time ago :-) It was for communicating with a DALLAS RTC DS1337.

Is your code better than this one ? I mean will it run faster ?

Because I didn't use the MODULO 10, here is what I did:

char bin2BCD8(char cValue)
{
char cDig10=0;
char cDig1=0;
char cTemp;
cTemp=cValue; // Backup the value
do{
cTemp=cTemp-10;
if(cTemp<0)
{
break;
}
else
{
cDig10++;
}
}while(1);
cDig1=cValue-(cDig10*10);
cDig10=(cDig10<<4)|cDig1;
return cDig10;
}

Hi

unsigned char chartobcd(unsigned char n)
{
  return ((n / 10) << 4) | (n % 10);
}

the above should be

unsigned char chartobcd(unsigned char )
{
  if (n >99) crash();
  return ((n / 10) << 4) | (n % 10);
}

Hi,

WOW I'm learning from the PRO...your code seems very compact.

I will try it. But will I get a packed BCD value ?

I'll get back to you if I have some problems.

Thank you,

Adi,

Hi
If a want to write a BCD number to a RTC, I prefear to do that check in the input routine, and that because of the different of input values.

year = 00 - 99
month = 01 - 12
day = 01 - 31
hour = 0 - 23
min = 0 - 59
sec = 0 - 59

Ingvar

will I get a packed BCD value ?

Yes, by "ORing" the two halves of the number together, you get a single byte, two digit BCD number.

And now the add-on question for extra points: how many assembly instructions is the minimum this functionality can be achieved in? You may assume all inputs are already in the correct registers, and it doesn't matter where the output is, as long as it's somewhere.

But what is the more interesting value - the number of assembly instructions or code efficiency? A DIV and MODULO takes very long, so it might be better to use some add-and-compare loops

Jochen

A DIV and MODULO takes very long,

Indeed. And it's too many instructions, anyway ;-) So sorry, but no cigar yet.

if (n >99) crash();

The above line (or something akin to it) is used thousands of times in all Microsoft products. They of course document better so their equivalent would be.

/* Randomly screw the customer so they purchase an upgrade. *.
if (user_is_doing_something_important)
{
   crash_horribly_and_do_not_save();
}