315-4PN33

6 Deployment PtP communication
6.1 Fast introduction
With this CPU the integrated RS485 interface is fix set to PtP (point-
to-point) communication.
n PtP functionality
–
For operation there is no further configuration in the hardware
configurator required.
– Using the PtP functionality the RS485 interface is allowed to
connect via serial point-to-point connection to different source
respectively 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
6.2 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 | 315-4PN33 | GB | 14-43 83