Acyclic communication (DP/V1 and PCP)
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PHOENIX CONTACT
3-1
3
Acyclic communication (DP/V1 and PCP)
DP/V1
DP/V1 extends the cyclic data exchange function according to IEC 61158 to include acyclic
services. This makes it easy to operate even complex terminals.
PCP
PCP is used in the local bus to exchange data acyclically. This is usually the
parameterization data of complex terminals (e.g., IB IL RS 232) or variable length data.
DP/V1 is a mechanism which corresponds to PCP at PROFIBUS level. The
IL PB BK DI8 DO4/EF-PAC coupler prepares the data records, which are sent via DP/V1
from the Class 1 or Class 2 master, for the PCP mechanism in the local bus. PCP data from
the local bus is in turn converted into DP/V1 telegrams by the bus coupler.
The different communication types will be described in the following.
3.1
Acyclic communication via the Class 1 master
(C1 master)
C1 master
The C1 master carries out parameterization during slave startup and is also the master for
cyclic data traffic. It may also be necessary to read a parameter acyclically from the terminal
as an option using this C1 master.
Corresponding read and write access rights are therefore defined for the C1 master. As it
already has a connection to the slave during cyclic data traffic, the C1 master does not have
to establish an explicit connection (using "Initiate"), but can communicate with the slave
directly via "Read" and "Write".
3.2
Acyclic communication via the Class 2 master
(C2 master)
C2 master
For communication in the C2 master, the data fields are identical to those for C1
communication, and it is only the SAPs (Service Access Points) which differ. Additional
fields are "Initiate" and "Abort" to establish and release the connection via SAP49 and 50.
If DP/V1 terminals are already in use, the routines for connection management can be
adapted easily. The C2 master can be implemented in various forms, e.g., in the form of a
display device or operator interface. In a display device, the data is retrieved from the slave
on request if, for example, a specific parameter is to be read. Access to the operator
interface is usually acyclic.
Before programming the application, check whether your control system or configuration
tool supports DP/V1. If not, the functions can be used via the cyclic process data channel
(DP/V0), see Section 3.5 on page 3-13 and onwards.
Up to 16 terminals capable of PCP can be connected to the IL PB BK DI8 DO4/EF-PAC
bus coupler.