PDU (protocol data unit)

This is the central part of packets exchanged in S7-Communication. A PDU cosists of:
  • A 10 or 12 byte header
  • A parameter area
  • A data area
  • Header:
    Positionmeaningpossible values
    0allways 0x32
    1type1,2,3 or 7
    2,3unknown0
    4,5sequence number
    6,7length of parameters
    8,9length of data
    10,11error code
    Parameters:
    Positionmeaningpossible values
    0a function number
    restdepends on function number0,2,3 or 7
    Data:
    Positionmeaningpossible values
    0a function number
    restdepends on function number0,2,3 or 7