WAGO-I/O-SYSTEM 750 Appendix 75750-658 CAN GatewayManualVersion 1.2.0, valid from FW/HW-Version 01/0110.1.3 Communication PhasesThe Mailbox 2.0 mechanism defines two communication phases:• Synchronization• Data exchangeOnly after successful synchronization from sender to receiver the actual user datacan be exchanged.10.1.3.1 SynchronizationIn the synchronization phase, the handshake byte is used in Control mode.A distinction is made between interpretation as signaling mode and interpretationas command acknowledgement mode.In command acknowledgement mode, the handshake byte appears as follows:Status Nibble Control NibbleBit 3 Bit 2 Bit 1 Bit 0 Bit 3 Bit 2 Bit 1 Bit 00 Acknowledgement 0 CommandThe Control nibble is used to transfer a request while the Status nibble containsthe response to the request.10.1.3.1.1 Mailbox CommandsThe following commands are defined:Table 29: CommandsValue Explanation Description0 INVALID Signals that the sender has not started operations again after areset.1 HOLD REQUEST Notice that the channel is ready, but data is not currentlybeing transferred(e.g. because the output buffer is still empty)2 RESET REQUEST Prompt to reset3 ... 7 - (not supported, ignore)
