Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
21-1
21 S7 Communication
21.1 Common Parameters of the SFBs/FBs and SFCs/FCs
for S7 Communication
Classification
The parameters of communication SFBs/FBs for configured S7 connections can be
divided into the following five categories according to their functions:
1. Control parameters are used to activate a block.
4. Addressing parameters are used to address the remote communication partner.
5. Send parameters point to the data areas that are to be sent to the remote
partner.
6. Receive parameters point to the data areas where the data received from
remote partners will be entered.
7. Status parameters are used to monitor whether the block has completed its task
without error or for the analysis of any errors that have occurred.
Control Parameters
Data exchange will only be activated if the appropriate control parameters have a
defined signal state (for example are set) when the SFB/FB is called or when the
signal state has undergone a specific change since the previous SFB/FB call (for
example, positive edge).
Note on S7-300
For the first call, set the parameter REQ to FALSE.