IOF_LB_BreakLocationTest 1:

The IOF_LB_BreakLocationTest function block carries out a break location test in a Beckhoff Lightbus optical fiber ring and can locate possible break locations. If no break location is detected during the test, the output variable BOXNO returns the current number of Lightbus modules in the ring. If a break location is detected before the Nth module in front of the receiver input, the BREAK flag is set and the module number is provided via the output variable BOXNO. If the BOXNO variable returns a value of 0xFF the break location is situated immediately in front of the receiver input, and cannot be located.


    NETID     : T_AmsNetId;
    START     : BOOL;

NETID: The network address of the TwinCAT computer on which the function is to be executed can be entered here (type: T_AmsNetID). If it is to be run on the local computer, an empty string can be entered.

DEVICEID: DeviceId specifies the device on which the function is to be executed. The device IDs are specified by the TwinCAT system during the hardware configuration.

START: the block is activated by a positive edge at this input.

TMOUT: States the length of the timeout that may not be exceeded during execution of the command.


    BUSY     : BOOL;
    ERR      : BOOL;
    ERRID    : UDINT;
    BREAK    : BOOL;
    BOXNO    : WORD;

BUSY: When the function block is activated this output is set. It remains set until a feedback is received.

ERR: If an error should occur during the transfer of the command, then this output is set once the BUSY output was reset.

ERRID: Supplies the ADS error number when the ERR output is set.

BREAK: This flag is set if a break location is detected in the optical fiber ring.

BOXNO: The module number before the receiver input in front of which the break location has been detected.


Development environment

Target platform

IO hardware

PLC libraries to be integrated (category group)

TwinCAT v3.1.0

None. This functionality is not supported by TwinCAT 3 at present!

Beckhoff Lightbus Master: C1220 ISA; FC200x PCI

Tc2_IoFunctions (IO)