SHL

Overview

IEC operator for bitwise left-shift of an operand.

erg:= SHL (in, n)

in: operand to be shifted to the left

n: number of bits, by which in gets shifted to the left

NOTE: If n exceeds the data type width, it depends on the target system how BYTE, WORD, DWORD and LWORD operands will be filled. Some cause filling with zeros (0), others with n MOD <register width>.

NOTE: The amount of bits which is considered for the arithmetic operation depends on the data type of the input variable. If the input variable is a constant, the smallest possible data type is considered. The data type of the output variable has no effect at all on the arithmetic operation.

Examples

See in the following example in hexadecimal notation the different results for erg_byte and erg_word. The result depends 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

PROGRAM shl_st
VAR
 in_byte : BYTE:=16#45; (* 2#01000101 )
 in_word : WORD:=16#0045; (* 2#0000000001000101 )
 erg_byte : BYTE;
 erg_word : WORD;
 n: BYTE :=2;
END_VAR
erg_byte:=SHL(in_byte,n); (* Result is 16#14, 2#00010100 *)
erg_word:=SHL(in_word,n); (* Result is 16#0114, 2#0000000100010100 *)

Example in FBD

 

 

Example in IL

LD     in_byte
SHL    2
ST     erg_byte