ability of a system that, by adequate technical or organizational measures, prevents from hazards either deterministically or by reducing the risk to a tolerable measure

Note 1 to entry: Equivalent to functional safety

values which are issued or delivered instead of process values when the safety function is set to a fail-safe state

Note 1 to entry: In this document, the fail-safe substitute values (FSV) are always set to binary “0”.

a one-bit value used to indicate a certain status or control information.

a globally unique identifier (GUID) is a 128-bit number used to identify information in computer systems. The term universally unique identifier (UUID) is also used. In this document, UUID version 4 is used.

a means used to ensure the correct order among transmitted safety PDUs and to monitor the communication delay. The MNR starts at a random value and is incremented with each request. It rolls over to a minimum threshold value that is not zero.

Note 1 to entry: Instance of sequence number as described in IEC 617843.

Note 2 to entry: The transmitted MNR is protected by the transmitted CRC signature of the ResponseSPDU.

a predicate meaning that the respective object is a “standard” object and has not been designed and implemented to fulfill any requirements with respect to functional safety.

non-safety-related part of the implementation of this document which maps the SPDU to the actual OPC UA services. Depending on which services are used (e.g. Client/Server or PubSub), different mappers can be specified.

input and output data (in a safety PDU) that are required to control an automated process

Qualifier is an attribute (bit or Boolean), indicating whether the corresponding value is valid or not (e.g. being a fail-safe substitute value).

A communication partner in a unidirectional safety link. A SafetyAutomationComponent can be a SafetyProvider (data source), a SafetyConsumer (data sink), or both.

Entity (usually software) that implements the data sink of a unidirectional safety link.

application data transmitted across a safety network using a safety protocol

Note 1 to entry: The safety communication layer does not ensure the safety of the data itself, but only that the data is transmitted safely.

Entity (usually software) that implements the data source of a unidirectional safety link.

Randomly generated authenticity ID which is used to safely authenticate SafetyProviders having the same SafetyProviderID.

Note 1 to entry: Together with the SafetyProviderID, it is the instance of connection authentication as described in IEC 617843.

User-assigned, locally unique ID which is used to safely authenticate SafetyProviders within a certain area. All SafetyProviders within this area may share the identical SafetyBaseID.

Note 1 to entry: Together with the SafetyBaseID, it is the instance of connection authentication as described in IEC 617843.

the part of the transmission system (implemented in hardware and software) that is not implemented according to any safety standards. This document is using the services of the standard transmission system to transmit prebuilt safety packets.