Bus Topology; Features Of Dp (Distributed Periphery); Rapid Cyclical Transmission With Ppo Using Dp - Danfoss FCM 300 Operating Instructions Manual

Bus topology

Single master operation with DP V0

Features of DP (Distributed Periphery)

- Is used by several PLC manufacturers for remote
peripheral I/O communication.
- 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 telegramme size.
- Occupies I/O memory space in PLC proportional
to the number of slaves employed, which may

Rapid Cyclical transmission with PPO using DP

6
FCM 300 / FCD 300 / VLT
®
2800 / DP V1 PROFIBUS
- Single master
- 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 Read - using PCV channel
6. Parameter Write - using PCV channel
7. Read parameter description - using PCV channel
limit the number of participants. Additional data
require additional I/O memory space.
DP should be used when fast cyclical process control
is needed. Such a concept would typically call
for single master 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
alternative it is of course possible to close the
control loop outside the bus.
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