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Entry type: FAQ Entry ID: 38051505, Entry date: 12/01/2015

With which devices can the S7-1200 communicate via the integrated PROFINET interface and which protocols does the S7-1200 support?

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This entry shows how many simultaneous, asynchronous communication connections the S7-1200 CPU supports.

Communication partners of the S7-1200
The S7-1200 CPU communicates with the devices below via the integrated PROFINET interface:

  • Other S7-CPUs (S7-200, S7-300, S7-400, S7-1200 and S7-1500)
  • Programming devices
  • HMI devices (like SIMATIC Basic Panels and SIMATIC Comfort Panels)
  • Devices which support open user communication

Maximum number of simultaneous, asynchronous communication connections
The S7-1200 CPU supports the following maximum number of simultaneous, asynchronous communication connections:

Connection type Description and max. number of connections
Open user communication The S7-1200 CPU supports 8 connections for open user communications (active or passive) using the following instructions: T_SEND_C, T_RECV_C, TCON, TDISCON, TSEND and TRECV.

Modbus TCP uses Open User Communications (OUC) connections as Modbus communications path. There can be multiple client-server connections in addition to the connection between STEP 7 and the CPU. Mixed client and server connections are supported up to the maximum number permitted to be supported by the CPU for Open User Communications.

S7 communication
  • 3 connections for a passive S7-1200 CPU communicating with an active S7 CPU or LOGO!, this means the S7-1200 is S7 server. The active S7 CPU or LOGO! establishes the connection and uses PUT and GET instructions (S7-300, S7-400, S7-1200 and S7-1500) or the ETHx_XFER instruction (S7-200) to read and write data.
  • 8 connections for an active S7-1200 CPU communicating with a passive S7 CPU or LOGO!, this means the S7-1200 is S7 client. The active S7 CPU establishes the connection and uses the PUT and GET instructions to read and write data.
HMI connections

Firmware V2 and V3
The S7-1200 CPU provides dedicated HMI connections to support up to 3 HMI devices.

Firmware V4
With Firmware V4 and higher the S-1200 CPU supports max. 12 HMI connections. Depending on the type and model of the HMI device and the HMI functions used, each HMI device can actually use 1, 2 or 3 connection resources. There is guaranteed support of 4 HMI devices. Independent of the number of available connection resources used it might be possible to use more than four HMI devices simultaneously.

PG connections The S7-1200 CPU provides connections to support 1 programming device (PG).
Web server connections (HTTP) The S7-1200 provides connections for the web server.

Table 1

Fig. 1


  • S7-1200 CPU with firmware version V2.02 to V2.2
    For PROFINET the S7-1200 CPU supports a maximum of 8 PROFINET IO devices and 128 submodules, whichever is reached first. PROFIBUS supports a maximum of 16 DP slaves on one DP master with a maximum of 256 submodules per DP slave.
    A maximum of 16 DP slaves and IO devices altogether is supported.
  • S7-1200 CPU with firmware version V3.0 or higher
    With firmware version V3.0 and higher the S7-1200 CPU supports 16 PROFINET IO devices with a maximum of 256 submodules. PROFIBUS supports 32 DP slaves with a maximum of 512 submodules per DP slave.

Integrated PROFINET interface of the S7-1200
The integrated PROFINET interface of the S7-1200 CPU is implemented as an RJ45 socket.

Fig. 2

Supported protocols
The S7-1200 supports the following protocols via the integrated PROFINET interface:

Protocol Firmware version
TCP V1.0
ISO on TCP (RFC 1006) V1.0
UDP V2.0
PROFINET RT - Basic Services and IO Controller V2.0
S7 Communication (S7 Server) V1.0
S7 Communication with the PUT/GET instructions (S7 client) V2.0
Web server V2.0
Modbus TCP V2.1
HTTP - Hyper Text Transfer Protocol V2.0
HTTPS - Hyper Text Transfer Protocol Secure V2.0
SNMP - Simple Network Management Protocol V2.0
LLDP - Link Layer Discovery Protocol V2.0
DCP - Discovery & Configuration Protocol V2.0
NTP - Network Time Protocol V2.0
ARP - Address Resolution Protocol V2.0

Table 2

Further Information
More information about communication with the S7-1200 CPU is available in the S7-1200 manual in Entry ID: 91696622.

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