XPS-E
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Poll Mode
In this mode XPS-E returns with every data_exchange the data
received up to the present time. Apart from the receive data and their
lengths a receive data number is entered into the telegram. This
confirmation number is automatically incremented if new receive data
is available in the telegram. If the receive telegram does not contain
new data (data length = 0), the confirmation number remains
unchanged.
NOTICE
If this mode is used when the Master is generating a Process Image
according to a Poll List it must be paid attention that this Poll List can
be read quickly enough as with every data_exchange the process
image will be overwritten. This may cause loss of data on part of the
application. Loss of data can be noticed when the confirmation
number is not subsequent.
Illustration 3:
Data Reception in Poll Mode
x= Receive Request Number
S= Status
The telegrams mentioned above can either be started automatically
by the Master (cyclically during automatic polling) or by the
application.
NOTICE
The receive request number (X) in Poll Mode may not be set.
Data exchange