Limit 1 and Limit 2

Limit 1 ad Limit 2, index 0x80n0:13, index 0x80n0:14

If the limits of the values that can be entered in indices 0x80n0:13 and 0x80n0:14 are violated, the bits in indices 0x60n0:03 and 0x60n0:05 are set accordingly (see sample below). The indices 0x80n0:07 or 0x80n0:08 serve to activate the limit value monitoring.

Output limit n (2-bit):

Limit 1 and Limit 2 1:

Limit evaluation

The limit evaluation assumes a signed representation. The conversion to the desired representation (index 0x80n0:02) only takes place after the limit evaluation.

Limit 1 and Limit 2 2:

Linking in the PLC with 2-bit values

    • PLC:
      IEC61131-PLC contains no 2-bit data type that can be linked with this process data directly. In order to transmit the limit information, therefore, define an input byte, e.g.
      Limit 1 and Limit 2 3:

      and link the limit to the VariableSizeMismatch dialog as described in the chapter Process data.
    • Additional task
      2-bit variables can be created in the System Manager.
      Limit 1 and Limit 2 4:
      Linking of 2-bit variable to additional task

    Sample

    Channel 1; Limit 1 and Limit 2 enabled, Limit 1 = 2.8 V, Limit 2 = 7.4 V, representation: signed integer

    Entry in index (Limit 1): 0x8000:13
    (2.8 V / 10 V) x 216 / 2 - 1 = 9,174dec

    Entry in index (Limit 2): 0x8000:14
    (7.4 V / 10 V) x 216 / 2 - 1 = 24,247dec

    Output:

    Input channel 1

    Index 0x6000:03

    Index 60x6000:05

    1.8 V

    0x01hex, (Limit 1, limit value undershot)

    0x01hex, (Limit 2, limit value undershot)

    2.8 V

    0x03hex, (Limit 1, limit value reached)

    0x01hex, (Limit 2, limit value undershot)

    4.2 V

    0x02hex, (Limit 1, limit value exceeded)

    0x01hex, (Limit 2, limit value undershot)

    8.5 V

    0x02hex, (Limit 1, limit value exceeded)

    0x02hex, (Limit 2, limit value exceeded)

    Swap Limit index 0x80n0:0E

    The limit function can be inverted by SwapLimitBits in index 0x80n0:0E.

    Output Limit n (2-bit):

    SwapLimitBits setting

    Value

    FALSE (default setting)

    • 0: not active
    • 1: value < limit value
    • 2: value > limit value
    • 3: Value is equal to the limit value

    TRUE

    • 0: not active
    • 1: value > limit value
    • 2: value < limit value
    • 3: Value is equal to the limit value