NORD Drivesystems BU0020 - Manual (Page 48)

PROFIBUS DP – Supplementary manual options for NORD - Frequency Inverters
48 BU 0020 GB-2612
Each PROFIBUS DP system can consist of a wide range of different devices. These are divided into
three different device classes:
Device class Description
DP master Class 1 (DPM1) This master controls the cyclic reference data traffic, i.e. process data is
automatically exchanged with the DP slaves (I/Os) in a repetitive
sequence. Typical devices for central control are memory-programmed
control units (PLCs) or PCs.
DP master Class 2 (DPM2) These masters are engineering, planning or operating devices (OP,
touch-panels). They can also access the bus acyclically and additionally
enable the configuration and parameterisation of intelligent field devices
such as frequency inverters. A DPM2 master does not need to be
permanently present on the Profibus DP.
Slave Slaves are peripheral devices with a direct interface to the I/Os, such as
I/Os, drive units, valves, measurement transducers, frequency inverters
etc., which read in input information and output information to the
peripheral devices.
Table 8: Device classes
Fig. 5: Communication, device classes
PROFIBUS DP is specially designed for production automation and uses the RS485 standard as the
transfer method. RS485 is the most commonly used transfer method and enables transfer rates of up
to 12 MBaud. A shielded twisted wire cable is used.
PROFIBUS DP is designed both for rapid time-critical applications as well as for complex
communication tasks. Some of the fundamentals of PROFIBUS DP and its further technical
developments (performance levels) are briefly summarised below.
For the transfer of 512 bit input and 512
bit output data divided over 32 bus
participants, the PROFIBUS DP requires
approx. 1ms with a transfer rate of 12
Mbit/s.
Fig. 6: Diagram of bus cycle time
DP Slave 1 DP Slave 2 DP Slave 3
PROFIBUS
DP Master Class 1
PROFIBUS
DP Master Class 2
Token
DP Slave 4