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BACnet Insight

2024 zusammen mit allen Auslegungen und Errata für diesen Standard, die möglicher- 5.2.2. Link_Speed Property
weise zutreffen.
Wenn die referenzierte Klausel oder Tabelle in 135-2020 und 135-2024 identisch ist, 5.2.2.1. Protocol_Revision 18 through 23
wird nur die Klausel 135-2024 referenziert. For devices claiming PR 18 through 23 the Link_Speed property is required in all NPOs
with Protocol_Level equal to PHYSICAL. See 135-2020, Table 12-73.
5. Choosing a Protocol_Revision
NOTE: The Link_Speed property is required in a non-hierarchical NPO where the
Choosing the Protocol_Revision for your device depends on several factors and Network_Type supports a Protocol_Level is equal to PHYSICAL as specified in 135-
dependencies. 2020, Table 12-73. Because of property inheritance, the equivalent topmost NPO is
ƒ A derivative device where the parent device claims PR 18 through 23 may want to also required to support the Link_Speed property.
remain at a lower PR to reduce the time to market.
ƒ If the BACnet Secure Connect data link is being added to a device that has already NOTE: The Link_Speed property is required in a non-hierarchical NPO with Network_
been BACnet tested, claiming a PR less than 24 is allowed and may reduce the time Type equal to MSTP. See 135-2020, Table 12-73.
to market.
ƒ If a device supports the BACnet Secure Connect data link and the Secure Connect NOTE: Interpretation IC-135-2020-5 clarified that the Link_Speed property is not
NPO, PR 24 or greater must be claimed. required in every NPO.
ƒ New devices should consider claiming PR 24 or greater to avoid additional develop-
ment in the future. 5.2.2.2. Protocol_Revision 24
As of PR 24, the Link_Speed property is only required in NPOs with Protocol_Level
5.1. Protocol_Revision 17 equal to PHYSICAL and Network_Type equal to SERIAL. See 135-2024, Table 12-71.9.
135-2012 Addendum ai (PR 17) added support for the NPO. Slightly over a year later,
135-2012, Addendum bf (PR 18) significantly changed the functionality of an NPO and NOTE: The Link_Speed property is required in a non-hierarchical NPO with Network_
resolved several fundamental issues found in the original PR 17 version of the NPO. Type equal to MSTP.

NOTE: PR 17 is not recommended in any existing or new products. 5.2.3. Allowed Properties

5.2. Protocol_Revision 18 and 24 Differences 5.2.3.1. Protocol_Revision 18 through 23
Addendum cc to 135-2020 (PR 24) added the Secure Connect NPO and changed sev- For devices claiming PR 18 through 23, an NPO is allowed to contain properties that are
eral requirements that affect all NPOs. The below clauses describe the differences not part of its Network_Type. For example, an NPO with Network_Type equal to MSTP
between a device claiming PR 18 through 23 and PR 24 or greater. could contain the IP_Subnet_Mask property. See 135-2020, Clause 12.56.

5.2.1. Property Inheritance (Hierarchical NPOs) 5.2.3.2. Protocol_Revision 24
As of PR 24, NPOs cannot contain any properties from any other Network_Type. A hier-
5.2.1.1. Protocol_Revision 18 through 23 archical NPO can only contain properties specified in its protocol level. See 135-2024,
For devices claiming PR 18 through 23 that contain hierarchical NPOs, property inher- Clause 12.56.1.1.
itance is required. Property inheritance requires the topmost NPO to contain all prop-
erties from its lower level NPOs and any changes to a property at one level must be 5.2.4. Reference_Port Property
reflected in the topmost level.
Property inheritance has the benefit of allowing clients to read and write all network port 5.2.4.1. Protocol_Revision 18 through 23
settings by accessing just the topmost NPO in a hierarchy of NPOs. For devices claiming PR 18 through 23, the Reference_Port property is allowed to be
Writable properties, including inherited properties, must be writable in the topmost absent or equal to 4194303 to indicate an NPO at Protocol_Level equal to BACNET_
NPO. These inherited writable properties can be, but are not required to be, writable in APPLICATION or NON_BACNET_APPLICATION is a non-hierarchical NPO.
the lower level source NPO.
If a property is writable in a lower level NPO it must be writable in the topmost NPO. 5.2.4.2. Protocol_Revision 24
When inherited properties are written, in either the lower level or the inheriting NPO, the As of PR 24, the Reference_Port must be absent to indicate an NPO at Protocol_Level
values must be written through to the other NPO. equal to BACNET_APPLICATION or NON_BACNET_APPLICATION is non-hierarchical.

NOTE: If a property is specified in multiple NPOs in the hierarchy chain, the property’s NOTE: If the Reference_Port is equal to 4194303, it is considered an unconfigured
value in the NPO nearest to the top of the chain is the value reflected in the topmost hierarchical NPO.
NPO. See 135-2020, Clause 12.56.10.1.1.
5.2.5. Additional_Reference_Ports Property (Hierarchical NPOs)
NOTE: NPOs at Protocol_Level equal to PROTOCOL cannot inherit any properties from The Additional_Reference_Ports property was added in Addendum cc to allow an NPO
referenced NPOs. See 135-2020, Clause 12.56.10.1.1. to reference more than one lower level NPO. A device must claim PR 24 or greater to
support this property.
5.2.1.2. Protocol_Revision 24
As of PR 24 a device is not allowed to support property inheritance so the topmost
NPO cannot contain any properties from its lower level NPOs. See 135-2024, Clause
12.56.1.1.

44 BACnet Europe Journal 44 03/26