BECKHOFF DK9222-1109-0015 - Manual (Page 3)

I/O
Wireless Automation
Application Note DK9222-1109-0015
KM6551 – operating modes: PTP, star, broadcast
With​the​three​operating​modes​of​the​KM6551​data​exchange​terminal,​10​bytes​of​process​data​can​be​exchanged​
independently​of​the​higher​level​fieldbus​or​transmitted​via​radio​between​two​independent​controllers.​With​the​KM6551​
Bus​Terminal​Beckhoff​offers​a​cost‑effective,​high‑performance​option​for​establishing​PTP,​star​and​broadcast​configurations​
via​radio.
​
Master
Slave
send output data
send input data
Option 1 | Data exchange peer-to-peer
Master
Slave 1 Slave 2 Slave 3 Slave 4 Slave 5 Slave 6 Slave 7
Option 2 | Data exchange up to max. 7 devices
Master
Slave 1 Slave 2 Slave 3 Slave 4 Slave 5
...
Slave x
Option 3 | Broadcast up to x devices
Fig. 1 KM6551: operating modes PTP (left), star (centre) and broadcast (right)
In​PTP​mode​(peer‑to‑peer),​two​independent​controllers​communicate​bidirectionally​with​each​other​and​exchange​10‑byte​
input​and​output​data​cyclically.​The​complete​exchange​takes​20 ms.​The​free‑field​distance​between​two​KM6551​units​can​be​
up​to​300 m​in​PTP​mode.
In​star​mode,​the​master​communicates​unidirectionally​with​up​to​seven​slaves;​the​10 bytes​of​process​data​are​distributed​
cyclically​to​all​devices​and​the​exchange​takes​20 ms​per​slave.​The​slaves​are​directly​addressed​by​the​master,​so​that​the​
temporal​sequence​of​the​communication​is​programmed​from​the​PLC.
In​broadcast​mode,​the​master​sends​new​data​to​all​broadcast​slaves​unidirectionally​in​a​10 ms​cycle.​The​slaves​receive​
these​data,​but​cannot​send​any​data​themselves.​Any​number​of​slaves​can​listen​in.
New Automation Technology Beckhoff
For​application​notes​see​disclaimer​on​the​last​page