Convert 32byte to 8 byte

neurus · Joined: 31 Mar 2004 Posts: 23 Location: Switzerland

hi

I want to convert a variable with 32 bytes into 4 variables with 8 bytes, because I've to save the data into the eeprom.
I'm working with a Pic 18F252 and CCS.

Thank you

Pablo

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

I assume you mean to convert a 32 BIT variable to 4 variables of 8 BITS each. Check out the functions make8() and make32().
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Ttelmah · Guest

Ttelmah · Guest

As a general note, As SherpaDog points out, there are make8, and make32 functions, but the advantage of the union, is it involves no data movement at all. If you have the union declared, and write variable.b[0] to the eeprom, the compiler generates a single byte fetch, from the original variable, making this very efficient.
The union, will also wrk on other compilers, when the makex functions, are CCS specific.

Best Wishes

neurus · Joined: 31 Mar 2004 Posts: 23 Location: Switzerland

hi

thank very much. Just what I looked for!

Aloha

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Ttelmah · Guest

The 'make8' function, approximates the action of the union. However the make32, involves moving the four bytes into four seperate variables, adding a second set of variables, and an extra data movement.

Best Wishes