Presentation of the Library

 

General Information

Library Overview

The PreventaSupport library provides the FB_PreventaDiag and FB_PreventaMain function blocks to be used for diagnostic and maintenance purposes with Preventa XPS safety modules.

Preventa XPS safety modules provide the auxiliary output Z1. At Z1, a bit sequence signal is delivered which encodes diagnostic device information relating to the device. For details on this module output, refer to the corresponding user manual listed in the section Related Documents.

When connected to a standard controller input or a suitable input device, the bit sequence signal can be used as an input signal for the FB_PreventaDiag function block. FB_PreventaDiag decodes the bit sequence sent from the device and outputs a diagnostic code as shown in section Status Output at q_dwStatus.

This diagnostic code can be forwarded to the FB_PreventaMain function block. Based on the diagnostic code, FB_PreventaMain executes calculations concerning the maintenance and life cycle of the Preventa XPS safety module and the devices (sensors/actuators) connected to the module.

General Considerations

The diagnostic bit sequence output by the Preventa XPS safety module is composed of 10 bits with a duration of 200 ms each. In order to detect the entire bit sequence correctly, the cycle time of the task that executes the function blocks must be less than or equal to 50 ms.

NOTE: The function blocks must only be used in a cyclic task and they are to be executed in each task cycle.

NOTE: The entire bit sequence has a length of two seconds (10 x 200 ms). Status changes which occur during a running sequence are only transmitted in the following sequence. If such status changes do not last until the next sequence starts (that is, if several changes occur within two seconds), they are not encoded in the bit sequence. In this case, they cannot be detected by the FB_PreventaDiag function block. As a consequence, the operating cycle counter may miss operating cycles.

NOTE: If several input devices are connected to a Preventa XPSUDN or XPSUS safety module, the operating cycle counter may miss operating cycles under the following circumstances: If one connected input device has switched to the inactive state but not yet back to the active state and further connected input devices perform switching operations in the meanwhile.

NOTE: Switching off the Preventa XPS safety module is detected by the library with a delay of up to eight seconds.

NOTE: Switching off the Preventa XPS safety module may cause the FB_PreventaDiag function block to detect an incorrect status information.

NOTE: If the time period between the inactivation and the following reactivation of a connected input device (as part of a proof test) is shorter than two seconds, the proof test counter may not be reset.

Characteristics of the Library

The table indicates the characteristics of the library:

NOTE: For this library, qualified-access-only is set. This means that the POUs, data structures, and constants have to be accessed using the namespace of the library. The default namespace of the library is Preventa.