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| embedded_systems:ethercat:understanding_ethercat:understanding_sync_with_dc [2019-01-11 09:30] – mgehrig2 | embedded_systems:ethercat:understanding_ethercat:understanding_sync_with_dc [2019-02-13 11:22] – mgehrig2 | ||
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| Zeile 1: | Zeile 1: | ||
| ====== Understanding Synchronisation with Distributed Clocks ====== | ====== Understanding Synchronisation with Distributed Clocks ====== | ||
| ===== Additional Documentation ===== | ===== Additional Documentation ===== | ||
| - | TODO | + | * [[https:// |
| + | * [[https:// | ||
| ===== The Sync0 Synchronisation Signal ===== | ===== The Sync0 Synchronisation Signal ===== | ||
| In a DC system each participant has its own clock which is synchronized with all other clocks. | In a DC system each participant has its own clock which is synchronized with all other clocks. | ||
| - | The Sync0 event is triggered synchronously | + | The Sync0 event is triggered synchronously |
| ==== The Sync0 Event ==== | ==== The Sync0 Event ==== | ||
| The Sync0 event ist triggered on all devices of the network at the same time. | The Sync0 event ist triggered on all devices of the network at the same time. | ||
| - | The slaves can read inputs and set outputs after a deterministic and configurable time after the Sync0 event. | + | The slaves can read inputs and set outputs after a deterministic and configurable time (1C32:06 + 1C32: |
| Thus it is possible that all outputs in the whole network are set simultaneously within nanoseconds. | Thus it is possible that all outputs in the whole network are set simultaneously within nanoseconds. | ||
| + | The same is true for reading inputs at a determenistic time. | ||
| It is also possible to set the outputs with a desired time delay. | It is also possible to set the outputs with a desired time delay. | ||
| + | |||
| + | {{ : | ||
| ==== DCM Master Shift Mode ==== | ==== DCM Master Shift Mode ==== | ||
| Zeile 39: | Zeile 44: | ||
| ===== Example Setting and Read with a ELMO EtherCAT Slave ===== | ===== Example Setting and Read with a ELMO EtherCAT Slave ===== | ||
| - | {{ : | + | ==== 1000usec cycle ==== |
| - | This example shows the flow of a signal through an EtherCAT network. | + | {{ : |
| + | |||
| + | This example shows the flow of a signal through an EtherCAT network | ||
| - The application sets a signal (e.g. a torque signal) which is forwarded from the Acontis stack to the EC bus. | - The application sets a signal (e.g. a torque signal) which is forwarded from the Acontis stack to the EC bus. | ||
| - The stack sends the EC frame after the application is finished. | - The stack sends the EC frame after the application is finished. | ||
| Zeile 51: | Zeile 58: | ||
| - After the next Sync0 event the application can evaluate the signal. | - After the next Sync0 event the application can evaluate the signal. | ||
| + | ==== 250usec cycle ==== | ||
| + | |||
| + | {{ : | ||
| + | This example shows the flow of a signal through an EtherCAT network with an elmo Gold Twitter and a cycletime of 250usec. | ||
| + | |||
| + | Most of the lag is due to slow copy and write operations of the Gold Twitter controller. | ||
| + | Another motor controller may be faster. | ||
| + | |||
| + | The delay marked with the circle may be omitted. | ||
| + | Depending on the timing of the EtherCAT frame the data will be sent in the same cycle. | ||
| + | |||
| + | ==== Notes to bandwith ==== | ||
| + | The bandwith of EtherCAT is 100MBit/ | ||
| + | If a large part of the bandwidth is used, then the transmission of the EtherCAT frame takes almost the entire period. | ||
| + | This can lead to an additional latency of one period. | ||
| + | |||
| + | |||
| + | ===== Appendix ===== | ||
| + | {{: | ||