Splitting a 16 bit word into two 8 bit bytes

Guest · Posted: Thu Dec 21, 2006 9:19 am

Hi,

I need to write a 16 bit variable to the internal EEPROM. I know that I can use the Make16 function to recombine two 8 bit bytes into one 16 bit word, but I can't find a reverse function. How do I split the 16 bit word into two 8 bit bytes?

Thanks

Augie

jamesjl · Joined: 22 Sep 2003 Posts: 52 Location: UK

The answer is to use make8(); This is from the manual:

davekelly · Joined: 04 Oct 2006 Posts: 53 Location: Berkshire, England

I use the following style, which can be expanded to accomodate 32 bit numbers as well

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Davekelly,

Your code can be optimized. Working with pointers (16 bit) is not very efficient in a 8 bit PIC processor, also the increments in the last line of WriteEEPROM16 have no purpose.

Here an optimized version (now 34 bytes, was 84 bytes in the original)

Guest · Posted: Fri Dec 22, 2006 10:33 am

Hi All,

OK, getting back to my original question, I seem to be having a problem with make8 and make 16. The problem is that these functions don't seem to work correctly in both directions. In other words if I use make8 to "de-contruct" a 16 bit word, and then use make 16 to "reconstruct" the I don't end up with the same value Crying or Very sad

Ttelmah · Guest

You have byte 0, and byte 1, the wrong way round when you reconstruct the word...
The high byte comes first in make16.
A an 'aside', I prefer the use of a union, to the make8/mae16 functions, since this is portable C to other compilers, and also makes it much easier to keep the bytes in the right order. There is no need to actually have seperate variables at all with this: