Danfoss VLT PROFIBUS DP MCA 101 User Manual

5.2.1 PROFIBUS DP-V1 Introduction
The PROFIBUS DP extension DP-V1 oers acyclic communi-
cation in addition to the cyclic data communication of DP
V0. This feature is possible using a DP master class 1 (for
example, PLC), as well as a DP master class 2 (for example
PC Tool).
Cyclic communication means that data transfer takes place
continuously with a certain refresh rate. This function is the
known DP V0 function normally used for quick updates of
I/O process data.
Acyclic communication is a
one-o data transfer event,
used for read/write from and to parameters from process
controllers, PC-based tools, or monitoring systems.
5.2.2 Features of a Master Class 1
Connection
•
Cyclic data exchange (DP-V0).
•
Acyclic read/write from and to parameters.
A master class 1 is used as the process controller (either
PLC or PC-based), responsible for commands, speed
reference, status of the application, and so on. The master
class 1 acyclic connection can be used for general
parameter access in the slaves. However, the acyclic
connection is xed and cannot be changed during
operation.
5.2.3 Features of a Master Class 2
Connection
•
Initiate/abort acyclic connection.
•
Acyclic read/write from and to parameters.
The master class 2 acyclic connection is typically used for
conguration or commissioning tools for easy access to
each parameter in any slave in the system. The acyclic
connection can be dynamically established (initiated) or
removed (aborted) even when a master class 1 is active on
the network.
5.2.4 Services Overview
Master
type
Service
Read Write Data
trans-
port
Initiate Abort Alarm
Read
data
from
slave
Write
data to
slave
Read
and
write
data
Open a
connec-
tion
Close a
connec-
tion
Master
class 1
Yes Yes Yes – – –
Master
class 2
Yes Yes Yes Yes Yes –
Table 5.1 Services Overview
5.2.5 Principle of Data Exchange by
PROFIBUS DP-V1
In a DP cycle, the master class 1 (MC1) rst updates the
cyclic process data for all slaves in the system. The MC1
then sends 1 acyclic message to 1 slave. If a master class 2
(MC2) is connected, the MC1 hands over the bus rights to
MC2. MC2 is then allowed to send 1 acyclic message to 1
slave. The token is then handed back to the MC1, and a
new DP cycle begins.
Illustration 5.1 DP Cycle
•
MC: Master class.
•
C1...Cn: Cyclic data.
•
AC1: Acyclic data master class 1.
•
AC2: Acyclic data master class 2.
PROFIBUS DP services are activated via specic service
access points (SAP). Table 5.2 shows the SAP specied for
acyclic communication.
Parameter Access
VLT
®
PROFIBUS DP MCA 101
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Danfoss VLT PROFIBUS DP MCA 101 Specifications

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Brand	Danfoss
Model	VLT PROFIBUS DP MCA 101
Category	Media Converter
Language	English