XPS-E
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4 Data exchange
4.1 Send Data
To send data via XPS-E onto a serial end device, the send flag of
XPS-E must be reset (ref. Communication Status, Bit 0 = 0), as
otherwise the send data to XPS-E will be discarded. For a send job,
the following data must be included into the telegram.
– Send job number. This job number must be different for each send
procedure. Reasonably, the value should be incremented by 1 at every
send procedure.
– Send data length. If the data length is set to 0, no data is sent via the
serial interface. Otherwise this byte includes the number of the following
user data.
– Send data (user data)
4.2 Receive Data
XPS-E has a 2Kbyte receive data buffer to temporarily store data
received from the connected serial end device. For data transfer to
the PROFIBUS-DP Master the operating modes Poll mode and
Request-Mode are available. The mode will be selected during
parameterization of XPS-E by the Master (See Chapter„s
[
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10]et_prm Parameterization“, Section „DP-Data Transmission
Mode“). In the Poll mode available receive data will be sent at every
data_exchange.req with the corresponding data_exchange.res from
XPS-E to the PROFIBUS-DP Master. In the Request mode the XPS-
E sends this data only if in data_exchange.req a defined byte has
been changed (the receive request number). Thus, the polling of
existing receive data can be controlled by the Master.
The request mode is recommended for Masters that are polling the
slaves cyclically to generate a process image. (application may be
too slow to process the current data of the process image).
Data exchange