PLC Programming

Bit-Shift Operators
NOT
Bitwise NOT of a bit operand. The operand should be of the type BOOL, BYTE, WORD or DWORD.
Example in IL:
Var1 :BYTE;
LD 2#1001_0011
NOT
ST Var1 (* Result is 2#0110_1100 *)
Example in ST:
Var1 := NOT 2#1001_0011
Example in FBD:
10.3 Bit-Shift Operators
SHL
Bitwise left-shift of an operand : erg:= SHL (in, n)
in gets shifted to the left by n bits. If n > data type width, for BYTE, WORD and DWORD will be filled
with zeros. But if signed data types are used, like e.g. INT, then an arithmetic shift will be executed in
such cases, that means it will be filled with the value of the topmost bit.
Note:
Note:
Please note, that the amount of bits, which is regarded for the arithmetic operation, is pretended by
the data type of the input variable !. If the input variable is a constant the smallest possible data type
is regarded. The data type of the output variable has no effect at all on the arithmetic operation.
See in the following example in hexadecimal notation that you get different results for erg_byte and
erg_word depending on the data type of the input variable (BYTE or WORD), although the values of
the input variables in_byte and in_word are the same.
Example in ST:
10-6 CoDeSys V2.3