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7
Deployment PtP communication
7.1 Fast introduction
Per default, the RS485 interface of the CPU is used for PROFIBUS
DP master. Via hardware configuration the RS485 interface may be
switched to
p
oint-
t
o-
p
oint (PtP) communication via the Parameter
Function RS485 X3
of the
Properties
.
n
PtP functionality
– Using the PtP functionality the RS485 interface is allowed to
connect via serial point-to-point connection to different source
res. target systems.
The protocols res. procedures ASCII, STX/ETX, 3964R, USS and
Modbus are supported.
The parametrization of the serial interface happens during runtime
using the FC/SFC 216 (SER_CFG). For this you have to store the
parameters in a DB for all protocols except ASCII.
The FCs/SFCs are controlling the communication. Send takes place
via FC/SFC 217 (SER_SND) and receive via FC/SFC 218
(SER_RCV). The repeated call of the FC/SFC 217 SER_SND
delivers a return value for 3964R, USS and Modbus via RetVal that
contains, among other things, recent information about the acknowl-
edgement of the partner station. The protocols USS and Modbus
allow to evaluate the receipt telegram by calling the FC/SFC 218
SER_RCV after SER_SND. The FCs/SFCs are included in the con-
signment of the CPU.
The following FCs/SFCs are used for the serial communication:
FC/SFC
Description
FC/SFC 216
SER_CFG
RS485 parameterize
FC/SFC 217
SER_SND
RS485 send
FC/SFC 218
SER_RCV
RS485 receive
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 buffer (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.
General
Protocols
Parametrization
Communication
Overview FCs/SFCs for
serial communication
Overview
VIPA System 300S
Deployment PtP communication
Principle of the data transfer
HB140 | CPU-SC | 313-6CF13 | GB | 15-50
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