Adding to an existing index

[usmank6009]

I’m trying to implement the logic below:
if bcc = STX or bcc = CR, then bcc := +1 (increment of 1).
bcc is a byte and i’m trying to increment it by 1 if this condition above is true.
my code is:
IF message_byte[11] = 16#0D OR message_byte[11] = 16#02 THEN
message_byte[11] := message_byte[11] + TO_BYTE(1);
END_IF

Variable :Message_byte. Type: AXL_RSUNI_ARR_B_1_1023. This type is ( ARRAY[1..1023] OF BYTES)
where message_byte is an array of bytes and I want to access a specific one. However, it gives me an error when saying it can’t be added.
any help is appreciated

[Martin_PLCnext_Techn]

The error message indicates that the addition operator can only be used on ANY_NUM types. The elements of message_byte are not ANY_NUMs (they are ANY_BITs).

One solution is to cast the byte variable to an ANY_NUM type for the addition operation, and then cast it back to a BYTE for the assignment: