SERCOS III
| Sercos III | |
 |
|
| Year created: | 2003 |
| No. of devices: | 511 |
| Speed | 100 Mbit/s |
| Hotplugging? | Yes |
| Redundancy? | Yes |
| Ethernet compatibility? | Yes |
| Governing Body: | Sercos International e.V. |
| Website: | http://www.sercos.com |
Sercos III is the third generation of the Sercos interface, a globally standardized open digital interface for the communication between industrial controls, motion devices, input/output devices (I/O), and Standard Ethernet nodes. Sercos III merges the hard real-time aspects of the Sercos interface with Ethernet. It is based upon and conforms to the Ethernet standard (IEEE 802.3 & ISO/IEC 8802-3). Work began on Sercos III in 2003, with vendors releasing first products supporting it in 2005. In addition to the standard Sercos features cited under the Sercos interface general description, Sercos III also provides:
In order to achieve the throughput and jitter requirements required in the applications the interface is designed for, Sercos III operates primarily in a Master/Slave arrangement exchanging cyclic data between nodes. The Master initiates all data transmission during a Sercos real-time cycle. All data transmissions begin and end at the Master (circular).
Communication across a Sercos III network occurs in strict cyclic intervals. A cycle time is chosen by the user for a given application, ranging from 31.25 µs to 65 ms. Within each cycle, data is exchanged between Sercos III nodes using two types of telegrams: MDTs and ATs (see Telegram Types). After all MDTs and ATs are transmitted, Sercos III nodes allow the remaining time in the cycle to be used as an UC (Unified Communication) Channel, which can be used to exchange data using other formats, such as IP.
The network remains available to UCC traffic until the next cycle begins, at which time the Sercos III nodes close the nodes to UCC traffic again. This is an important distinction. Sercos is purposely designed to provide open access at all ports for other protocols between cyclic real time messages. No is required. This provides the advantage that any Sercos III node is available, whether Sercos III is in cyclic mode or not, to use other protocols, such as TCP/IP, without any additional hardware to process tunneling. Sercos nodes are specified to provide a store and forward method of buffering non-Sercos messages should they be received at a node while cyclic communication is active.
All Sercos III telegrams conform to the IEEE 802.3 & ISO/IEC 8802-3 MAC (Media Access Control) frame format.
...
Wikipedia