Operating instructions

Acyclical communication takes the form of a once-off data transfer event, mainly 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
- Cyclical data exchange (DP V0)
- Acyclical read/write from and to parameters
In general a master class 1 is used as the process controller (either PLC or PC-based), responsible
for commands, speed reference, status of the application, etc.. The master class 1 acyclical con-
nection can be used for general parameter access in the slaves. However, the acyclical connection
is fixed, and cannot be changed during operation.
5.2.3. Features of a Master Class 2 Connection
- Initiate / Abort acyclical connection
- Acyclical read/write from and to parameters
The master class 2 acyclical connection is typically used for configuration or commissioning tools
for easy access to each parameter in any slave in the SYSTEM. The acyclical connection can be
dynamically established (Initiate) or removed (Abort) even when a master class 1 is active on the
network.
5.2.4. Services Overview for FC 100, 200 and 300
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
connection
close a con-
nection
Master Class 1 yes yes yes - - -
Master Class 2 yes yes yes yes yes -
5.2.5. Principle of Data Exchange by PROFIBUS DP V1
In a DP cycle the master class 1 (MC1) will first update the cyclical process data for all slaves in
the SYSTEM. The MC1 can then send one acyclical message to one slave. If a master class 2 (MC2)
is connected, the MC1 will hand over the bus rights to MC2, which will then be permitted to send
one acyclical message to one slave. The token is then handed back to the MC1, and a new DP
cycle begins.
VLT
®
Profibus 5. How to Access the Parameters
MG.33.C4.02 - VLT
®
is a registered Danfoss trademark 45
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