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SA0147: Unusual shift operation – strict

Detects bit shift operations which are not made to bit field data types (BYTE, WORD, DWORD, LWORD)

Justification: The IEC 61131-3 standard permits bit access only to bit field data types. However, the CODESYS compiler also permits bit shift operations with unsigned data types.

Importance: Low

Tip

See also the strict rule SA0018.

Example 108. Example
PROGRAM PLC_PRG
VAR
    in_byte : BYTE := 16#45;    // 2#01000101
    in_word : WORD := 16#0045;    // 2#0000000001000101
    in_uint : UINT;
    in_dint : DINT;
    erg_byte : BYTE;
    erg_word : WORD;
    erg_uint : UINT;
    erg_dint : DINT;
    n: BYTE := 2;
END_VAR

erg_byte := SHL(in_byte,n);    // no error because BYTE is a bit field
erg_word := SHL(in_word,n);    // no error because WORD is a bit field
erg_uint := SHL(in_uint,n);    // SA0147
erg_dint := SHL(in_dint,n);    // SA0147

Output in the Messages view:

  • sa_icon_message.png SA0147: Unusual shift operation – strict



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