Communicating with S7-200

Introduction

Fernhill SCADA supports these types of connection to S7-200 PLC Devices:

You can connect Fernhill SCADA directly to an S7-200 PLC Device using a standard RS-485 adapter:

Setup Notes:

The RS-232 connection from the computer running Fernhill SCADA to the RS-232 to RS-485 Adapter should include the TXD, RXD and RTS signals.
The RS-232 to RS-485 adapter must be configured for 2-wire mode, where the transmitter is enabled by an active RTS signal.
Use Profibus cable (or equivalent) to connect the S7-200 PLC to the RS-485 Adapter. A standard Profibus connector simplifies the connection to the S7-200 PLC. RS-485 adapters have four screw terminal connections often marked RX+, RX-, TX+, TX-. Connect the Profibus Red conductor to the RX+ and TX+ terminals, connect the Profibus Green conductor to the RX- and TX- terminals.
Termination resistors should be used at both ends of the Profibus cable.
For best reliability, the RS-232 port should be a direct peripheral port on the computer running Fernhill SCADA. Use of USB connected serial ports can introduce inter-character delays, which can result in communication dropouts.
Use the Siemens S7 PPI Autodetect Wizard to automatically discover the correct communication parameters and configure Fernhill SCADA.

To manually configure Fernhill SCADA for direct connection to an S7-200 PLC:

Create a Siemens S7 PPI Channel Tag
The Mode settings of the Siemens S7 PPI Channel Tag should be configured to: Baud=9600 Parity=E Data=8 Stop=1 RTS=Tg. The Baud=9600 option matches the default baud rate of S7-200 PLC Devices. The RTS=Tg option tells the serial port hardware to make the RTS signal active during transmit.
Create a Siemens S7 Serial PLC Tag that references the channel.

You can connect Fernhill SCADA to S7-200 PLC Devices using a PPI adapter:

General Setup Notes:

When connecting to a single S7-200 PLC, the PPI - RS485 connection of the PPI Adapter can be connected directly to the S7-200 PLC.
When connecting more than one S7-200 PLC, use standard Profibus cable (or equivalent) to connect the PLC Devices together. Fit one Profibus connector with a programming port, and connect the PPI - RS485 connection of the PPI Adapter to that connector.
Use the Siemens S7 PPI Autodetect Wizard to automatically discover the correct communication parameters and configure Fernhill SCADA.

To manually configure Fernhill SCADA for connection to S7-200 PLC Devices using a PPI adapter:

Create a Siemens S7 PPI Channel Tag
The Mode settings of the Siemens S7 PPI Channel Tag should match the setup of the adapter. See the tables below for the appropriate Mode settings and adapter switch settings
Create a Siemens S7 Serial PLC Tag that references the channel.

Setup Notes for 6ES7 901-3CB30-0XA0:

There are 8 switches on the side of the 6ES7 901-3CB30-0XA0 adapter labelled SW1 to SW8. To work with Fernhill SCADA the switch settings need to be setup correctly.
SW1, SW2 and SW3 on the PPI Adapter define the communication speed of the RS-232 port. These switches should match the Mode settings of the Siemens S7 PPI Channel Tag. The Mode setting should be set to Baud=nnnn Parity=E Data=8 Stop=1, where nnnn is chosen to match SW1 to SW3:

Baud SW1 SW2 SW3

Baud=115200 1 1 0

Baud=57600 1 1 1

Baud=38400 0 0 0

Baud=19200 0 0 1

Baud=9600 0 1 0
SW5 should be set to '0' (Freeport Mode). SW6 should be set to '0' (DCE Mode). SW7 should be set to '0' (11 Bit).

Setup Notes for 6ES7 901-3BF21-0XA0:

There are 6 switches on the side of the 6ES7 901-3BF21-0XA0 adapter labelled SW1 to SW6. To work with Fernhill SCADA these switch settings need to be setup correctly.
SW1, SW2 and SW3 on the PPI Adapter define the communication speed of the RS-232 port. These switches should match the Mode settings of the Siemens S7 PPI Channel Tag. The Mode setting should be set to Baud=nnnn Parity=E Data=8 Stop=1, where nnnn is chosen to match SW1 to SW3:

Baud SW1 SW2 SW3

Baud=115200 0 0 0

Baud=57600 0 0 0

Baud=38400 0 0 0

Baud=19200 0 0 1

Baud=9600 0 1 0
SW4 should be set to '0' (11 Bit Mode). SW5 should be set to '0' (DCE Mode). SW6 should be set to '0' (RTS on always).

You can connect Fernhill SCADA to an S7-200 PLC using an Ethernet module:

Fernhill SCADA supports these S7-200 Ethernet modules:

For a detailed overview of setting up an S7-200 Ethernet module refer to Siemens S7-200 Ethernet Connection Guide.

If the S7-200 module is configured, you can use the Siemens S7 TCP Autodetect Wizard to try and locate the PLC on the network.

To learn how to configure tags for Siemens S7 PPI connected PLC Devices.

For how to configure an S7-200 Ethernet module and Fernhill SCADA to work together.

For how to search COM ports for Siemens S7 PLC Devices and automatically create tags for any PLC Devices found.

For how to search a network for Siemens S7 PLC Devices and automatically create tags for any PLC Devices found.

For information on the Siemens S7 Driver.

For information about other drivers available in Fernhill SCADA.

For the meaning of terms used in Fernhill SCADA.