GE VersaPoint IC220PBI002, Руководство пользователя

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GFK-1911B Chapter 8 Communications 8-17
8
PCP Communication Via Process Data (Class1 Master in DP/V0
Mode)
If the control system is not DP/V1-compatible, it is still possible to operate complex
devices using acyclic services within the process data, as described in this
section.
Mechanism for Transmission in the Process Data
The mechanism for transmitting parameter data with the application’s process
data is a Virtual C1 “module” (VC1 module), which can be set up in the I/O Station
configuration. The Virtual C1 module is not linked to a specific module in the I/O
Station. During active data exchange, the Virtual C1 module can be assigned
sequentially to different I/O Station modules with communications objects. This
makes it possible to exchange parameter data in parallel with process data.
The Virtual C1 module is listed in the Profibus-DP/V1 NIU’s GSD file as "PD-PCP
x words"). It must be configured in the first position after the NIU. It is not linked to
any hardware, so a module is not actually inserted.
Process Data Width of the Virtual C1 “Module”
The process data width occupied by the Virtual C1 module in the process data
channel can be selected from 4 to 16 words in increments of 2 words. If there are
sufficient free resources, a data width of up to 16 words can be used. Because the
user data can be up to 58 bytes (29 words) per communication, it may be
necessary to split the user data and transmit it in several steps.
This leads to:
– Start
fragment
– Continue fragment
– End fragment
– Error or abort fragment
Each fragment contains a service byte, which is used for the precise assignment
of the fragment. The individual fragments and the service byte are explained in
detail on the next page.