Multi Point Interface - Configuration

In order to communicate with an S7 PLC using MPI either a Siemens MPI Adapter V5.1 or a Deltalogic MPI Adapter (ACCON-MPI-Adapter) is required. This Adapter must be connected to a serial interface of the PC running the S7 driver.

Connection type

PG/OP or other connection.

COMPort

Com port (COM1 ... COMx).

MPI

MPI address (range 0-31).

The MPI address and the PLC address must not equal! Set the MPI address of the adapter. For example, if the MPI address of the PLC is "5" then it is not allowed to set the address of the adapter also to "5".

Timeout

Timeout for the connection. Note that you set the timeout high enough so that it is sufficient when bigger blocks are queried from the PLC.

Active

This check box is used in order to set the connection to the peripheral device active or inactive. You can deactivate a connection that is already created and configured. The connection data point is not deleted and can be reactivated at any time. The status display changes from "Connected" to "Not Active"; if a connection is deactivated.

State

Shows the status of the connection to the periphery. The following states are possible:

  • "Not Connected" (Connection to the peripheral device lost e.g. PLC was disconnected from the network)

  • "Connected" (Connected with the peripheral device)

  • "General Query" (General query runs)

  • "Not Active" (Device with the associated check box set to inactive).

GQ

The General query button triggers a general query on the selected connection. The next received data will be sent to WinCC OA (without consideration of low level comparison and smoothing). See also the config entry AutoGQ on the page Possible config entries of the S7 driver). The driver executes an automatic general query when establishing a connection and at a redundancy switch.

If the connection is broken because of a timeout error in case of bigger queries, increase the timeout e.g. to 30 seconds and set the config entry checkPollReqPending = 1. Other queries are of course blocked during this time. Thus, set the useConnections = 3 or if enough connections are not available, the bigger block can be divided into several poll groups with the same interval.

For using MPI the config entry mpiDevice has to be specified in the config file. The config entry defines the parameter for one serial interface/adapter.

The configuration data of S7 MPI is shown below. The address of the data in the PLC is independent from whether the PLC is accessed via TCPIP or MPI.

The relevant configuration information is shown in the following table:

Parameter Change Mode Range DPE (_S7_Config)
Serial Interface Index Selectable in panel COM1…COMx IPAddress
PLC MPI address Selectable in panel 0-31 Slot
Serial baud rate Config file

38400 for Siemens Adapter

115200 for Deltalogic Adapter

Connection type Selectable in panel

PG/OP/Other 512/513/514

(Bit 9 is used to determine if it is a S7 MPI connection)

ConnectionType
Timeout Selectable in panel Like S7 TCPIP Timeout
PC address Config file 0-31
Single master flag Hard coded 1
Bus rate Hard coded 187500
Highest station address Hard coded 31
Profile Hard coded MPI

Currently only one PLC per MPI Adapter is supported. If more PLCs must be accessed, one adapter and one serial interface are required per PLC.

Redundant connection or redundant PLC modes are not supported for a MPI device. Redundant WinCC OA is only supported if the PLCs have more than 1 independent MPI interfaces.

One access to the PLC lasts approximately 50ms for the Deltalogic and 100ms for the Siemens Adapter. Therefore, in the first case 20 and in the latter 10 requests per second are possible.

MPI Configuration Example

To communicate with a PLC, enter the following configuration configuration:

  1. In the config file, define an MPI device by adding:

[s7]

mpiDevice = "COM1" 15 38400

In this case a Siemens Adapter will be connected to COM1 and 15 should be used as an MPI address for the adapter. The panel settings for the PLC are shown in the figure below. The entry of the COM port must match the device defined in the config file. The field MPI means the MPI address of the PLC.

Figure 1. S7 MPI Configuration