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XPS/XPS-E User's Manual
3.2.1 Poll Mode
In this mode XPS/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.
Note:
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.
PROFIBUS Data Traffic
DP-Master
X
XPS/XPS-E
TE
DATA_EXCHANGE.REQ
DATA_EXCHANGE.RES
Receive Buffer
XPS/XPS-E
S 1 2 TE
STDAT
X
S 2 5 STDAT
X
S 2 0
EN
EN
X
S 3 2 EN
X = Receive Request Number
S = Status
Figure 4: Data Reception in Poll Mode
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