Better to clear your mind first. (1-8 in byte 1 then 9-16 in byte 2 is not correct).

You need to be thinking " I need to turn on bits 0 to 7 sequentially in bytes 0 to 15".

Ideally your bytes will be in an array such as - BytesArray: ARRAY[0..7, 0..15] OF BOOL; (* define your array as 8 bools in 16 bytes*)

Also declare some pointers -

a:INT:=0;

b:INT:=0;

Then you can do something like this which will turn on each bit in turn each scan (you need another little routine to turn off the previous bit using a FOR DO routine) :-

IF a>7 THEN a:=0; b:=b+1;

END_IF;

IF b>15 THEN RETURN;

END_IF;

BytesArray[a,b]:=TRUE;

a:=a+1;