Communication
11.2 PROFINET
S7-1200 Programmable controller
962 System Manual, V4.2, 09/2016, A5E02486680-AK
From the STEP 7 Network view, you can create a complex communication topology by
connecting devices in different S7 subnets. You can connect classic CPUs and CPs as well
as the latest S7 CPUs and CPs and can include HMIs and PC stations such as an OPC
server.
Once you decide which devices must communicate and establish the necessary connections
using STEP 7, the Engineering System (ES) can download the corresponding routing tables
to the various S7 routers as part of the hardware configuration. After you download the
routing tables to the various S7 routers, the ES or other communication partners can
communicate with each device even though the devices are on different S7 subnets. This is
possible because the CPUs and/or CPs, in between, act as S7 routers. The CPUs and/or
CPs forward incoming connection requests to the next S7 router until the connection request
reaches the targeted device, and the devices establish the S7 connection.
The CPU uses the write record mechanism to transfer the routing tables required by the CP
devices in the local base. The routing tables establish the route from one device to another
at the time of a connection request, which includes a remote S7 Subnet_ID. The device
receiving the connection request interrogates its routing table, finds the next station in the
path to the target S7 subnet, and forwards the connection request. Eventually, the
connection request reaches the intended target and the response traverses the route in the
reverse direction.
The S7-1200 CPUs have a single PN interface and up to three CP devices connected to the
local communication bus. Therefore, you have two options for routing within the S7-1200
station:
● Routing between the CPU and a CP
● Routing from one CP to another CP
Refer to S7-1200 CPs at Siemens Industry Online Support, Product Support for further
information on all S7-1200 CPs that support the S7 routing function. The CP 1243-1
(https://support.industry.siemens.com/cs/us/en/view/584459) is shown as an example CP
module search for S7 routing capabilities.
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