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6 Commissioning | Reading and writing data objects on IO-Link devices
35 Manual Communication module UR20-4COM-IO-LINK 2547720000/03/09.2019
6.9 Reading and writing data objects on
IO-Link devices
Protocol for acyclic accesses
If you want to read and write IO-Link data objects
only during commissioning, we recommend us-
ing the IO-Link Configurator (see Chapter 7).
In order to access data objects for a field device (FD),
e.g.those of a IO-Link device, you must create a client appli-
cation (client app) for the fieldbus master (FB_M). This client
application communicates with a server on the u-remote
station (FBC/IO_M). The server communicates with the field
device application (FD app) on the field device.
An acyclic access to an IO-Link device always begins with
a write access by the client application to the server (acy-
clic-write.req). The data written determine which request is
sent by the server to the IO-Link device application (write.req
oder read.req).
The client application then performs a sequence of read ac-
cesses (acyclic-read.req). Provided that the IO-Link device ap -
plication has not yet processed the request, the server feeds
back that the IO-Link device application is busy (acyclic-read.
res with status “Busy”). If the server has received a response
from the IO-Link device application (write.conf or read.conf),
the server then forwards the response to the client applica-
tion (acyclic-read.res with status “Done” or “Error”).
For integrating the IO-Link with PROFIBUS and
PROFINET, also refer to the integration guidelines
of the PROFIBUS user organisation.
– IO-Link Integration Part 1: Technical Specifica -
tion for PROFIBUS and PROFINET
– IO-Link Integration – Edition 2: Guideline for
PROFINET
Client app
Serv
er
FB_M FBC/IO-M FD
FD app
data
data
write_data.res
/ with data
acyclic-read.req
acyclic-read.res
/ without data
write.conf
/ without data
/ “resource busy“
acyclic-read.req
acyclic-read.res
/ without data
/ Resource busy
/ “resource busy“
acyclic-read.req
acyclic-read.res
/ without data
/ Resource busy
acyclic-write.req
acyclic-write.res
/ without data
/ with data
write.req
/ with data
write_data.req
Writing a data object on an IO-Link device
Client app
Serv
er
FB_M FBC/IO-M FD
FD app
data
data
read_data.res
/ with data
acyclic-read.req
acyclic-read.res
/ without data
read.conf
/ with data
/ “resource busy“
acyclic-read.req
acyclic-read.res
/ without data
/ Resource busy
/ “resource busy“
acyclic-read.req
acyclic-read.res
/ without data
/ Resource busy
acyclic-write.req
acyclic-write.res
/ without data
/ with data
read.req
/ without data
read_data.req
Reading a data object on an IO-Link device