Siemens SIMATIC S7-400 Configuration And Use Manual page 77

SFCs for S7 Basic Communication via an S7 Station
You can access all communication partners that can be addressed via the I/O
addresses of a station (e.g. FM 355) with these communication SFCs. The links to
the communication partners are dynamically established when the SFCs are
called. A connection configuration is not necessary.
SFC
SFC 72 I_GET
SFC 73 I_PUT
SFC 74 I_ABORT
SFBs for S7 Communication (Configured S7 Connections)
These SFBs can be used to realize acknowledged data transmission via
configured S7 connection. The communication functions are not limited to data
transfer, additional functions can be used to control and monitor the
communication partner. Communication is only possible within an S7 project.
The communication SFBs can be categorized in four function classes:
Send and receive functions
You can use these communication SFBs to transfer data between two
communication partners. Approximately 400 bytes of data can be transferred.
SFB
SFB 8 USEND
SFB 9 URCV
SFB 12 BSEND
SFB 13 BRCV
SFB 14 GET
SFB 15 PUT
SFB 16 PRINT
Control functions
Using these SFBs, you can control the operating status of a communication
partner.
Automation System S7-400 Configuration and Use
A5E00442711-02
Interfaces, Networks and Data Communication for the S7-400
This SFC can be used to read a variable from a communication partner
without having to place a corresponding SFC in the communication partner.
This SFC can be used to write a variable to a communication partner without
having to place a corresponding SFC in the communication partner.
This SFC can be used to abort an existing link to a communication partner
without having to transfer variables. This allows the corresponding link
resources to be released again on both sides.
Uncoordinated data transfer independent of the time taken to process the
communication function (URCV) by the communication partner (e.g.
operating and maintenance signals). The data can be overwritten with more
up-to-date data at the communication partner.
Transfer of a data block to the communication partner. This means that data
transmission is complete only when the receive function (BRCV) in the
communication partner has accepted the data.
Program-controlled reading of variables without the need for additional
communication functions in the user program of the communication partner.
Program-controlled writing of variables without the need for additional
communication functions in the user program.
Sends data to a printer.
Description
Description
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