VIPA 313-6CF03, Manual, Page: 129 / 152

Manual VIPA System 300S SPEED7
Chapter 6 Deployment PtP communication
HB140E - CPU SC - RE_313-6CF03 - Rev. 07/45 6-7
Principals of the data transfer
The data transfer is handled during runtime by using SFCs. The principles
of data transfer are the same for all protocols and is shortly illustrated in
the following.
Data that is into the according data channel by the PLC, is stored in a FIFO
send buffer (
f
irst
i
n
f
irst
o
ut) with a size of 2x1024Byte and then put out via
the interface.
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 PLC.
If the data is transferred via a protocol, the adoption of the data to the
according protocol happens automatically.
In opposite to ASCII and STX/ETX, the protocols 3964R, USS and Modbus
require the acknowledgement of the partner.
An additional call of the SFC 217 SER_SND causes a return value in
RetVal that includes among others recent information about the
acknowledgement of the partner.
Further on for USS and Modbus after a SER_SND the acknowledgement
telegram must be evaluated by call of the SFC 218 SER_RCV.
Protocol FIFO Buffer
1024Byte
1024Byte
1024Byte
1024Byte
IN
OUT
RS485
Interface Program
SER_RCV
SFC 218
CFG
RECEIVE
SEND
SER_SND
SFC 217
SER_CFG
SFC 216
RS485 PtP communication
Overview
Principle