FCM 300 / FCD 300 / VLT
®
2800 / DP V1 PROFIBUS
■ Bus topology
S
ingle master operation with DP V0
-Singlemaster
- PLC communicates with telegrams of
constant length
- Fits to time critical requirements
Cyclical transmission (PLC)
1. Setpoint transmission
2. Actual value feedback
3. New set points computed
4. New set point transmission
5. Parameter Re ad - using P CV channel
6. Parameter Write - using PCV channel
7. Read parameter description - using PCV channel
■ Features of DP (Distributed Periphery)
- Is used by several PLC manufacturers for remote
peripheral I/O commun ication.
- Supports cyclical communication.
- SRD (Send Receive Data) service gives fast
cyclical exchange of process data between
master and slaves.
- Freeze and synchronize function is supported.
- Fixed data structure.
- Fixed telegram me size.
- Occupies I/O memory space in PLC proportional
to the number of slaves employed, which may
limit the number of participants. Additional data
require additional I/O memory space.
DP should be used when fast cyclical process control
is ne eded. Such a concept would typically call
for single m aster operation with a limited number
of slave stations. A high number of slaves will
increase the system response time.
This could also be the case where control
loops are closed over the bus. As a very fast
alternativeitisofcoursepossibletoclosethe
control loop outside the bus.
■ Rapid Cyclical transmission with PPO using DP Control of the drives during normal operation is often
very time critical, but it involves very few data, such
as control commands and speed reference. DP is
optimized for fast cyclical communication.
Parameter up-/downloads can be achieved by
using the PCV part of the so-called Parameter -
Process data Objects - PPO types 1, 2 or 5, see
drawing in paragraph PPO description.
MG.90.A5.02 - VLT is a registered Danfoss trademark
6
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