Communication   
3.3 S7 connections 
  CPU 31xC and CPU 31x, Technical Data 
3-30  Manual, 01/2006 Edition, A5E00105475-06 
See also 
Open communication via Industrial Ethernet (Page 3-24) 
3.3.3  Distribution and availability of S7 connection resources 
Distribution of connection resources 
Table 3-10  Distribution of connections 
Communication service  Distribution 
PG communication 
OP communication 
S7 basic communication 
In order to avoid allocation of connection resources being dependent only on 
the chronological sequence in which various communication services are 
requested, connection resources can be reserved for these services. 
For PG and OP communication respectively, at least one connection 
resource is reserved by default. 
In the table below, and in the technical data of the CPUs, you can find the 
configurable S7 connection resources and the default configuration for each 
CPU. You "redistribute“ connection resources by setting the relevant CPU 
parameters in STEP 7.  
S7 communication 
Other communication resources (e.g. via 
CP 343-1, with a data length of 
> 240 bytes) 
Available connection resources that are not specially reserved for a service 
(PG/OP communication ,  
S7 basis communication) are used for this. 
Routing PG functions 
(only for CPUs with DP/PN interface) 
The CPUs provide a certain number of connection resources for routing. 
These connections are available in addition to the connection resources. 
The subsection below shows the number of connection resources. 
Global data communication 
Point-to-point communication 
This communication service requires no S7 connection resources. 
PROFIBUS DP  This communication service requires no S7 connection resources. 
PROFINET CBA  This communication service requires no S7 connection resources. 
PROFINET IO  This communication service requires no S7 connection resources. 
Open communication by means of TCP/IP 
Open communication by means of ISO on 
TCP 
Open communication by means of UDP 
This communication service requires no S7 connection resources. 
Independently of the S7 connections, a total of 8 own resources are available 
for connections or local access points (UDP) for TCP/IP, ISO on TCP, UDP. 
SNMP  This communication service requires no S7 connection resources.