X20CM4800X - Data sheet V1.04
X2X Link communication cycles through 5 different steps to transfer a Flatstream sequence. At least 5 bus cycles are therefore required to successfully transfer the sequence.
Step I |
Step II |
Step III |
Step IV |
Step V |
|
Actions |
Transfer sequence from transmit array, increase SequenceCounter |
Cyclic matching of MTU and module buffer |
Append sequence to receive array Adjust SequenceAck |
Cyclic matching of MTU and module buffer |
Check SequenceAck |
Resource |
Sender (task to transmit) |
Bus system (direction 1) |
Recipient (task to receive) |
Bus system (direction 2) |
Sender (task for Ack checking) |
Fig.: Comparison of transfer without/with Forward
Each of the 5 steps (tasks) requires different resources. If Forward functionality is not used, the sequences are executed one after the other. Each resource is then only active if it is needed for the current sub-action.
With Forward, a resource that has executed its task can already be used for the next message. The condition for enabling the MTU is changed to allow for this. Sequences are then passed to the MTU according to the timing. The transmitting station no longer waits for an acknowledgment from SequenceAck, which means that the available bandwidth can be used much more efficiently.
In the most ideal situation, all resources are working during each bus cycle. The receiver still has to acknowledge every sequence received. Only when SequenceAck has been changed and checked by the transmitter is the sequence considered as having been transferred successfully.