Communication
77
Requests and responses between the IO device and the IO 
controller or the IO supervisor are transferred with the Record 
Data Objects. 
A write request is first sent containing the parameter request.
If the write request is valid, the RETA-02 acknowledges it with 
request accepted. The master should then send a read request. If 
the RETA-02 is still busy performing the internal parameter 
request, it will return a negative response with the error code 0xB5 
(State conflict). In this case, the read request will be repeated by 
the master until the RETA-02 has the PROFIdrive response data 
ready.
If the write request is invalid, a negative response is returned with 
an error code.
Master Record Data Object Slave
Parameter
processing
Parameter request
Parameter response
PROFIdrive Write request
Write response
without data
Read request
without data
Read response (–)
without data
Read request
without data
Read response
with data
Parameter request
PROFIdrive
Parameter response