Sorry for lame question, but what should I use to implement subj?

Nobody?

Then I ask visa versa (and more accurate).
I have string (for example): '47 4A 39', what should I do to convert it into string: 'G J 9'

At first the result string should be without spaces, i.e.: 'GJ9'.
at second you need procedure of type StrToNum and to parce the string byte by byte.

Another algo (simple and smaller, but not so flexible) is to:

1. Get first byte (for example 4).
1.1. if = 0 end of procedure.
2. subtract $30
3. if > $09 subtract 6
4. shift it 4 positions left -> value A
5. Get second byte
6. repeat 2 and 3 -> Value B
7. Byte = A or B-> store in output string
8. skip the string until <> space
9. goto 1.

Regards.

wery suitable solution, thank you

little correction: in step 3. substract 7, not 6

Right.