This article explains the fundamentals of BACnet gateways and how the protocols being used determine the BACnet Object types available in the gateway's configuration.
Intesis BACnet Protocol Gateways
Why doesn't my BACnet Server gateway allow Value object types such as AV, BV, and MV?
The object/data types available will depend on the gateway model. This question is sometimes asked when the wrong device was selected so you should evaluate whether your gateway should be a BACnet Client or Server device. If your gateway can't be configured to use a Value object type, this is not a missing feature but rather a limitation presented by the protocol used on the gateway's other interface.
Gateways that are a BACnet Client will be initiating communications directly with many types of BACnet Server devices. Because of this, it is prepared to read many BACnet object types that may be on those server devices such as BI, BO, AI, AO, Device, BV, AV, MI, MO, MV, NC, Schedule and Calendar BACnet objects (Please refer to your device's documentation for specifics).
Gateways that are a BACnet Server respond to Clients on the BACnet interface. The other protocol on some of these gateways may lack the equivalent data/object types that are used in BACnet. For example, Profinet has Input and Output data types but no Input/Output type that shares both read and write capabilities. This means that there is no equivalent to the BACnet Value object which features both read and write capabilities simultaneously. There would be no need to send a Value type to the Profinet network—only Input or Output types. In this case, the user would have to decide if the device is right for the application or have the Client on the BACnet network write the proper object type to the BACnet Server gateway so that it is compatible with Profinet data types.