Siemens S7-300 appendix Distribution and availability of S7 connection resources

Communication

3.3 S7 connections

3.3.3Distribution and availability of S7 connection resources

Distribution of connection resources

Table 3-10 Distribution of connections

Communication service	Distribution
PG communication	In order to avoid allocation of connection resources being dependent only on
OP communication	the chronological sequence in which various communication services are
S7 basic communication	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	Here you allocate connection resources which are still available and not
Other communication resources (e.g. via	reserved for a specific service (PG/OP communication, S7-based
CP 343-1, with a data length of	communication).
> 240 bytes)
Routing PG functions	The CPUs provide a certain number of connection resources for routing.
(only for CPUs with DP/PN interface)	These connections are available in addition to the connection resources.
	The subsection below shows the number of connection resources.
Global data communication	These communication services do not use connection resources.
Point-to-point communication
Open communication by means of TCP/IP	This communication service does not occupy any connection resources.
	Eight connections are available in parallel.
SNMP	This communication service does not occupy any connection resources.

CPU 31xC and CPU 31x, Technical data	3-29
Manual, Edition 08/2004, A5E00105475-05