Codesys sample program converting word variable into 2 byte variables

InstrumentationUK · Mar 7, 2014

Hi,
I am new to codesys programming and need some help converting a word variable into 2 byte variables.
If anyone provides the sample in Codesys syntax format, it would be great.
Thanks for the help.

InstrumentationUK · Mar 7, 2014

Any Idea folks !

jmsmoreira · Mar 7, 2014

Don't think the guys here like to do homework...

Gaz25 · Mar 7, 2014

http://www.plctalk.net/qanda/showthread.php?t=68817 may help

shooter · Mar 7, 2014

bijt1:=WORD_TO_BYTE(woord);
bijt2:=WORD_TO_BYTE(woord/256);

some other possibilities are www.oscat.de
codesys.com forum

as long as you put codesys in the subject i will find you.

kimao · Mar 10, 2014

shooter said:
bijt1:=WORD_TO_BYTE(woord);
bijt2:=WORD_TO_BYTE(woord/256);

some other possibilities are www.oscat.de
codesys.com forum

as long as you put codesys in the subject i will find you.

Shooter, could you please explain the theory behind why dividing by 256 would point to the high byte?

thanks

InstrumentationUK · Mar 11, 2014

Shooter ,,,could you please explain this division .

Ken Roach · Mar 11, 2014

Consider an ordinary integer, represented in binary.

Dividing that integer by 2 shifts all the bits to the right by 1 position.
Dividing that integer by 4 shifts all the bits to the right by 2 positions.

And so on. Dividing by 256 shifts all the bits to the right by 8 positions.

So dividing the original value by 256 shifts the value so that the High Byte is now in the position of the Low Byte.

An example:

1234 decimal = 04D2 (hex).

1234 / 256 = 4.8203125. Truncate the remainder.

Result = 04 (hex)

shooter · Mar 12, 2014

ken you are correct i should have used SHR (lazy)
bijt1:=WORD_TO_BYTE(woord);
bijt2:=WORD_TO_BYTE (SHR(woord,8));
this one works exactly.
wordtobyte just takes the lower 8 bits from the word.
shr means shifting the bits 8 times to the right, meaning the low byte is overwritten by the high one.
and wordtobyte does the same as above.

and instru take a piece of paper and make it in bits with 0 and 1

kimao · Mar 19, 2014

Thanks guys

Kim

Codesys sample program converting word variable into 2 byte variables

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