Communication
Acyclic data transfer
10
Networking via PROFIBUS−DP
10.3
10.3.3
L
10.3−3
EDSPM−TXXX−9.0−11/2009
10.3.3 Acyclic data transfer
The PROFIBUS−DP−V1 service can be used as an optional extension to enable an
acyclic parameter data transfer. PROFIBUS−DP−V0 and PROFIBUS−DP−V1 may
be operated simultaneously in one network.
The integration of the acyclic service in a fixed bus cycle depends on the correct
configuration of DPM 1:
l If configured, a time slot is reserved.
l If not configured, the acyclic service is added when a DP−V1 slave is
accessed acyclically with a DPM 2.
l The acyclic service always has lower priority.
Token
Master 1
(DPM 1)
Master 2
(DPM 2)
Slave 1 Slave 2 Slave 3
epm−t229
Fig. 10.3−2 Acyclic data transfer
Cyclic process data transfer between DPM 1 and slave 1 ... 3
Acyclic parameter data transfer between DPM 1 and slave 3
1. DPM 1 has the send authorisation (token) and communicates in a fixed
sequence with slave 1, then with slave 2 etc. up to the last slave of the
current list via the MS0 channel by means of request and response.
2. DPM 1 transfers the token to DPM 2.
3. During the remaining cycle time (time slot), DPM 2 establishes an acyclical
connection to one of the slaves in order to transmit parameter data via the
MS2 channel.
4. At the end of the running cycle time, DPM 2 returns the token to DPM 1.
– Depending on the remaining cycle time, several time slots may be required
for the acyclical data record transfer.
5. Once all of the data records have been transferred, DPM 2 establishes the
connection within one time slot.
) Note!
DPM 1 can perform the acyclical parameter data exchange via the
MS1 channel.
Parameter data transfer
between DPM 1 and slaves
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