Communicating With Modems

Setting Up the Communications Parameters When Using Modems

To set up communications parameters between your programming device or PC and the CPU when using modems, you must use the module parameter set for the PC/PPI cable. Otherwise, the Configure Modems function is not available. Ensure that the Configure Modems function is enabled, and then set up the configuration parameters by following these steps:

Note:

STEP 7-Micro/WIN 32 displays predefined modems in the Modem Setup dialog box. These modem types have been tested and verified to work with STEP 7-Micro/WIN 32 at the settings displayed.

Setting Up The Local Modem:

1.Select the menu command View > Communications (or click the Communications icon).

If the Communications Setup dialog box shows the PC/PPI cable icon, double click on the PC/PPI cable icon, and the Setting the PG/PC Interface dialog box appears. Go on to step 3.

If the Communications Setup dialog box does not show the PC/PPI cable icon, double-click the PC card icon or the top icon in the right-hand area. Go to step 2.

2.In the Setting the PG/PC Interface dialog box, select PC/PPI cable(PPI). If this selection is not in the list box, you must install it.

3.Click the “Properties” button. The PC/PPI cable(PPI) properties sheet for your CPU and modem appears. See Figure 8.

4.In the Properties - PC/PPI cable (PPI) sheet, click the Local Connection tab.

5.In the COM Port area, ensure that the Use Modem box contains a check mark. If the box is empty, select it to insert a check mark. See Figure 8.

6.Click the “OK” button. The Setting the PG/PC Interface dialog box appears.

7.Click the “OK” button. The Communications Setup dialog box appears. There are now two modem icons and a Connect Modem icon (see Figure 11).

Figure 11 Communications Setup Dialog Box

8.In the Communications Setup dialog box, double-click on the first modem icon. The Modem Setup dialog box for the local modem appears (Figure 12).

9.In the Local Modem area, select your modem type. If your modem is not listed, select the Add button to configure your modem. To do this, you must know the AT commands for your modem. Refer to the documentation for your modem.

10.In the Communications Mode area, select the communications mode (either 10-bit or 11-bit). The communications mode that you select depends upon your modem capabilities. (The 10-bit and 11-bit communications modes are described later in this section.) Both the local and the remote modem must have the same communications mode. Click the “Configure” button.

Figure 12 Modem Setup Dialog Box for the Local Modem

11.The Configure dialog box appears (Figure 13). If you are using a predefined modem, the only field that you can edit in this dialog box is the Timeout area. The timeout is the length of time that the local modem attempts to set up a connection to the remote modem. If the time indicated in seconds in the Timeout field elapses before the connection is set up, the attempt to connect fails. If you are not using a predefined modem, you must enter the AT command string for your modem. Refer to the documentation for your modem.

12.If you want to test the configuration of your local modem, click the “Program/Test” button while the modem is connected to your local machine (programming device or PC). This configures the modem to the current protocol and settings, and verifies that the modem accepts the configuration settings. Click ‘‘OK’’ to return to the Communications Setup dialog box.

13.Disconnect your local modem and connect your remote modem to your local machine (programming device or PC).

Figure 13 Local Modem Configuration

Setting Up The Remote Modem:

1.In the Communications Setup dialog box, double-click on the second modem icon (Figure 11). The Modem Setup dialog box for the remote modem appears (Figure 14).

2.In the Remote Modem area, select your modem type. If your modem is not listed, select the “Add” button to configure your modem. To do this, you must know the AT commands for your modem. Refer to the documentation for your modem.

3.In the Communications Mode area, select the communications mode (either 10-bit or 11-bit). The communications mode that you select depends upon your modem capabilities. (The 10-bit and 11-bit communications modes are described later in this section.) Both the local and the remote modem must have the same communications mode. Click the “Configure” button.

4.The Configure dialog box appears (Figure 15). If you are using a predefined modem there are no fields that you can edit. If you are not using a predefined modem, you must enter the AT command string for your modem. Refer to the documentation for your modem.

5.To test the configuration of your remote modem, click the “Program/Test” button while the modem is connected to your local machine (programming device or PC). This action transfers the parameters into a memory chip in the remote modem.

6.Click the “OK” button. The Communications Setup dialog box appears.

Figure 14 Modem Setup Dialog Box for Remote Modem

Figure 15 Remote Modem Configuration

7.Disconnect your remote modem from your local machine (your programming device or PC).

8.Connect the remote modem to your S7-200 programmable controller.

9.Connect your local modem to your programming device or PC.

Connecting the Modems:

1.To connect your modem, double-click on the Connect Modem icon in the Communications Setup dialog box. The Dial dialog box appears. See Figure 16.

2.Enter the phone number in the Phone Number field of the Dial dialog box.

3.To connect the local modem to the remote modem, click the “Connect” button.

4.Your modem setup is complete.

Figure 16 Connecting the Modems

Using a 10-Bit Modem to Connect an S7-200 CPU to a STEP 7-Micro/WIN 32 Master

Using STEP 7-Micro/WIN 32 on a PC / PG as a single-master device, you can connect to only one S7-200 CPU. You can use a Hayes-compatible 10-bit modem to communicate to a single remote S7-200 CPU.

You will need the following equipment:

·A single S7-200 CPU as a slave device. The CPU 221, CPU 222, CPU 224,CPU 226, and CPU226XM support the 10-bit format. Previous S7-200 CPUs do not support the 10-bit format.

·An RS-232 cable to connect the PC or SIMATIC programming device to a full-duplex,10-bit local modem

·A 5-switch PC/PPI cable (set to the proper baud rate, 10-bit data communications mode, and DTE mode) to connect the remote modem to the CPU

·An optional 9-pin to 25-pin adapter (if your modem connector requires it)

Note:

The 4-switch PC/PPI cable does not support the 10-bit format.

Figure 17 S7-200 Data Communications Using a 10-Bit Modem with a 5-Switch PC/PPI Cable

This configuration allows only one master device and one slave device. In this configuration, the S7-200 controller requires one start bit, eight data bits, no parity bit, one stop bit, asynchronous communication, and a transmission speed of 9600/19,200 baud. The modem requires the settings listed in Table 2. Figure 18 shows the pin assignments for a 25-Pin to 9-Pin Adapter.

Table 2 Modem Settings Required for a 10-Bit Modem        
Modem Data Format
in Bits
Transmission
Speed between Modem and PC
Transmission
Speed on
the Line
Other Features
10-Bit 8 data 9600 baud

19,200 baud

9600 baud

19,200 baud

Ignore DTR signal
  1 start
    No hardware flow control
  1 stop     No software flow control
  no parity      

Figure 18 Pin Assignments for a 25-Pin to 9-Pin Adapter

Using an 11-Bit Modem to Connect an S7-200 CPU to a STEP 7-Micro/WIN 32 Master

Using STEP 7-Micro/WIN 32 on a PC / PG as a single-master device as a single-master device, you can connect to one or more S7-200 CPUs. Most modems are not capable of supporting the 11-bit protocol.

Depending on whether you want to connect to only one S7-200 CPU or to a network of them (see Figure 19), you need the following:

·A standard RS-232 cable to connect the PC or SIMATIC programming device to a full-duplex,11-bit local modem

·One of the following PC/PPI cables:

-—A 5-switch PC/PPI cable (set to the proper baud rate, the 11- bit data communications mode, and the DTE mode) to connect the remote modem to the CPU

—A 4-switch PC/PPI cable (set to the proper baud rate) and a null modem adapter to connect the remote modem to the CPU

·If there are multiple CPUs connected to the remote modem, you will need a Siemens programming port connector on a PROFIBUS network.

Figure 19 S7-200 Data Communications Using an 11-Bit Modem with a 4 Switch PC/PPI Cable

This configuration allows only one master device and supports only the PPI protocol. In order to communicate through the PPI interface, the S7-200 PLC requires that the modem use an 11-bit data string. In this mode, the S7-200 controller requires one start bit, eight data bits, one parity bit (even parity), one stop bit, asynchronous communication, and a transmission speed of 9600/19,200 baud. Many modems are not capable of supporting this data format. The modem requires the settings listed in Table 3.

Figure 20 shows the pin assignments for a null modem adapter and a 25-Pin to 9-Pin Adapter

Table 3 Modem Settings Required for an 11-Bit Modem        
Modem Data Format
in Bits
Transmission
Speed between Modem and PC
Transmission
Speed on
the Line
Other Features
11-Bit 8 data 9600 baud

19,200 baud

9600 baud

19,200 baud

Ignore DTR signal
  1 start     No hardware flow control
  1 stop     No software flow control
  1 parity (even)      

Figure 20 Pin Assignments for a Null Modem Adapter and a 25-Pin to 9-Pin Adapter

See Also:

Communications Timeout