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Chapter 6 Deployment PtP communication
Manual VIPA System 300S SPEED7
6-12 HB140E - CPU SC - RE_313-6CF03 - Rev. 07/45
Communication
The communication happens via the send and receive blocks SFC 217
(SER_SND) and SFC 218 (SER_RCV).
The SFCs are included in the consignment of the CPU.
This block sends data via the serial interface.
The repeated call of the SFC 217 SER_SND delivers a return value for
3964R, USS and Modbus via RetVal that contains, among other things,
recent information about the acknowledgement of the partner station.
The protocols USS and Modbus require to evaluate the receipt telegram by
calling the SFC 218 SER_RCV after SER_SND.
Name Declaration Type Comment
DataPtr IN ANY Pointer to Data Buffer for sending data
DataLen OUT WORD Length of data sent
RetVal OUT WORD Return value (0 = OK)
Here you define a range of the type Pointer for the send buffer where the
data that has to be sent is stored. You have to set type, start and length.
Example:
Data is stored in DB5 starting at 0.0 with a length of
124Byte.
DataPtr:=P#DB5.DBX0.0 BYTE 124
Word where the number of the sent Bytes is stored.
At
ASCII
if data were sent by means of SFC 217 faster to the serial
interface than the interface sends, the length of data to send could differ
from the
DataLen
due to a buffer overflow. This should be considered by
the user program.
With
STX/ETX
,
3964R
,
Modbus
and
USS
always the length set in DataPtr
is stored or 0.
Overview
SFC 217
(SER_SND)
Parameter
DataPtr
DataLen