Burkert Type 8644 - Manual (Page 58)

54 - 8644/phoenix
S
YSTEM
D
ESCRIPTION
Communication via process data is a very widerspread method for accessing communication objects in E/
A modules and on the DPV1 field bus node. The standard for process data traffic is currently the Profibus
DP. DPV1 is a protocol expansion which is not yet available on all controls.
With the opportunity to access communication objects acyclically via cyclical process data, the DPV1 field
bus node can be used in every environment. Communication objects are therefore also readable from Stan-
dard C1 master that merely support the cyclical process data traffic.
Transmission in process data
Transmission in process data takes place via a virtual C1 module (VC1 module). This is a C1 module
because it, as is customary with E/A-Module modules, is selected in the hardware configurator and set in
the configuration/parameter telegram. This C1 module is only a virtual participant, since the process data
are used to transmit communication data (PCP). There are not tied to any specific module. During active
process data exchange it is possible to allocate the VC1 module sequentially exchange communication
data.
The process data width taken up by the VC1 module in the process data channel, can be chosen from 4 to
16 words in steps of 2 words each. You can therefore use the communication objects even when resources
are scare. When enough resources are free, you work with a data width of up to 16 words.
Elements of the VC1 module
Telegram construction for Request
Byte 1 Service
Byte 2 Module number
Byte 3 Index high
Byte 4 Index low
Byte 5 Sub-index
Byte 6 ... n Data block, if required
Telegram construction for Response
Byte 1: Service
Byte 2: Status
Byte 3 ... m Data block, if required
Service byte
A central function is held by the service byte. Since several transmissions may be necessary, depending
on the data width of the VC1 module, the service byte differentiates between fragments.
• Start fragment
• Continuation fragment
• Conclusion fragment
• Cancel / Error fragment
PCP via process data (PCP in DPV0)