7.2 Principle of the data transfer
The data transfer is handled during runtime by using FC/SFCs. The
principle of data transfer is the same for all protocols and is shortly
illustrated in the following.
n Data, which are written into the according data channel by the
CPU, is stored in a FIFO send buf
fer (first in first out) with a size
of 2x1024byte and then put out via the interface.
n When the interface receives data, this is stored in a FIFO receive
buffer with a size of 2x1024byte and can there be read by the
CPU.
n If the data is transferred via a protocol, the embedding of the data
to the according protocol happens automatically.
n In opposite to ASCII and STX/ETX, the protocols 3964R, USS and
Modbus require the acknowledgement of the partner.
n An additional call of the FC/SFC 217 SER_SND causes a return
value in RetVal that includes among others recent information
about the acknowledgement of the partner.
n Further on for USS and Modbus after a SER_SND the acknowl-
edgement telegram must be evaluated by a call of the FC/SFC
218 SER_RCV.
7.3 Deployment of RS485 interface for PtP
Per default, the RS485 interface is deactivated. Via hardware configu-
ration the RS485 interfaces may be switched to PtP operation (point
to point) via the parameter Function RS485 of the Properties.
Since the VIPA specific CPU parameters may be set, the installation
of the SPEEDBUS.GSD from VIPA in the hardware catalog is neces-
sary. The CPU may be configured in a PROFIBUS master system
and the appropriate parameters may be set after installation.
Overview
Activate RS485 to PtP
operation
Requirements
VIPA System 300S Deployment PtP communication
Deployment of RS485 interface for PtP
HB140 | CPU | 314-6CF03 | GB | 16-43 179
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