WAGO-I/O-SYSTEM 750
Appendix
81
750-657 IO-Link Master
Manual
Version 1.0.2, valid from FW/HW-Version 02/01
11.1.1.3.2 Data Exchange
In the data exchange phase, the handshake byte is used in Toggle mode. Because a
message is normally larger than the data part of the transmission channel, the
message must be transferred in several cycles (fragmentation).
Status nibble
Control nibble
Bit 3 Bit 2
Bit 1
Bit 0
Bit 3
Bit 2 Bit 1
Bit 0
1
T
0x00
1
T
0x00
Send fragment:
The first toggle bit expected by the IO-Link master after synchronization has the
value 0. The toggle bit in the second fragment receives a 1, the toggle bit in the
third fragment again a 0, etc. Only when the status of the toggle bit matches in the
received status nibble is receipt of the fragment confirmed by the IO-Link master.
Only then can a new fragment be sent. As long as there is no confirmation, the
fragment remains unchanged in the process image.
For the special case that the content of the send buffer is no longer sufficient to fill
the transmission channel completely, the transmission channel is filled with zeros
to the end.
Receive fragment:
The control now has to confirm receipt of this fragment. Receipt is confirmed by
inverting the toggle bit of the status nibble to be sent.
Because the Mailbox 2.0 mechanism can handle full duplex, sending and
receiving can occur simultaneously.
