CSN EN IEC 61158-4-21 ed. 2

CSN EN IEC 61158-4-21 ed. 2 (18 4020) The DLL provides basic time-critical data communications between devices in an automated environment. Type 21 provides priority-based cyclic and acyclic data communication using an internal collision-free, full-duplex dual-port Ethernet switch technology. For wide application in various automation applications, Type 21 does not restrict the cyclic/acyclic scheduling policy in the DLL.
Original English text of CSN EN Standard.
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