XPS/XPS-E User's Manual Contents
COMSOFT 15
3.1 Send Data
To send data via XPS/XPS-E onto a serial end device, the send flag of
XPS/XPS-E must be reset (ref. 4.2 Communication Status, Bit 0 = 0), as
otherwise the send data to XPS/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)
3.2 Receive Data
XPE/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 parameterisation of XPS/XPS-E by the Master
(ref. 2.4.3.5). In the Poll mode available receive data will be sent at every
data_exchange.req with the corresponding data_exchange.res
from XPS/XPS-E to the PROFIBUS-DP Master. In the Request mode the
XPS/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).
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