Siemens SIMATIC S7-1500 Function Manual page 314

Connection resources for routing
To transfer data beyond S7 subnets ("S7 routing"), an S7 connection is established between
two CPUs. The S7 subnets are connected via gateways known as S7 routers. CPUs, CMs
and CPs in S7-1500 are S7 routers.
The following applies for a routed S7 connection:
● A routed connection occupies one connection resource each in both end points. STEP 7
shows these connection resources in the "Connection resources" table.
● On the S7 router, two special connection resources are occupied for S7 routing. STEP 7
does not show the special connection resources for S7 routing in the "Connection
resources" table. The number of resources for S7 routing depends on the CPU. You will
find the resources for S7 routing in the technical specifications of the CPU in "Number of
S7 routing connections".
Figure 11-3
Data record routing also enables transfer of data beyond S7 subnets from an engineering
station connected to PROFINET to various field devices via PROFIBUS.
With data record routing, as with S7 routing, two of the special connection resources for
S7 routing are also occupied on every data record router.
Note
Connection resources with data record routing
With data record routing, on the data record router, two special connection resources for
S7 routing are occupied. Neither the data record connection nor the allocated connection
resources are displayed in the table of connection resources.
Communication
Function Manual, 11/2019, A5E03735815-AH
Connection resource for S7 communication
Special connection resources for S7 routing
Connection resources with S7 routing
Connection resources
11.2 Allocation of connection resources
313