BS EN IEC 61158-6-4:2019 Industrial communication networks. Fieldbus specifications Application layer protocol specification. Type 4 elements

Communication networks
Open systems interconnection
Bus networks
Industrial
Application layer (OSI)
Fieldbus
Communication procedures
Data transmission
Automatic control systems
Computer networks
Interfaces (data processing)
Process control

Link: BS EN IEC 61158-6-4:2019 Industrial communication networks. Fieldbus specifications Application layer protocol specification. Type 4 elements
Source: BSI Standards