VEGA VEGACOM 557 Profibus DP - Manual (Page 78)

78 VEGACOM 557 Profibus DP
Each Pr ofibus DP system consists of dif fer-
ent instrument types. Depending on their
individual tasks, the instruments can be clas-
sified into three types:
DP Master class 1 (DPM1)
This is a central control, exchanging in a
predetermined message cycle information
with the decentralised stations (DP Slaves).
Typical instruments ar e e.g. PLC, CNC or RC.
DP Master class 2 (DPM2)
Instruments of this type are programming,
planning or diagnostic instruments. They are
used for setup to create the configuration of
the DP system.
DP Slaves
A DP Slave is a peripheral instrument (sen-
sor/actuator), reading in input information and
outputting output infor mation to the peripher -
als. Instruments that only make input or out-
put infor mation are also possible. T ypical DP
Slaves are instruments with binary inputs/
outputs for 24 V or 230 V, analogue inputs,
analogue outputs, counters etc.
System reaction
The system reaction of Profibus DP has been
standardised to ensure large degree of in-
strument exchangeability. In general, this is
determined by the operating condition of the
DPM1. The DPM1 can be controlled by the
planning instrument either locally or via the
bus. There are three different (main) system
conditions, as the following explains:
Stop
There is no data traffic between the DPM1
and the DP Slaves.
Clear
DPM1 reads the input information of the DP
Slaves and keeps the outputs of the DP
Slaves in safe condition.
Operate
DPM1 is in the data transfer phase. The in-
puts of the DP Slaves are read in a cyclical
data traffic and the output information is
transferred to the DP Slaves.
M
Profibus DP mono-master system
DP Master (DPM1)
PLC
Profibus DP
Actor Sensor Drive
decentralised inputs and outputs
DP Slaves
Supplement C