PLC2U.com

Note! In the latest STEP 7-Micro/WIN Version 3.2 (or greater) the Modem handling has been revised.
As a result, this tip only applies to projects using Micro/Win versions prior to version 3.2

Special Hardware and Software Requirements:

One SIMATIC S7-200 (CPU 212 or higher)
One Siemens 5-switch PC/PPI cable (preferred). Order number 6ES7 901-3BF200-0XA0
One Siemens 4-switch PC/PPI cable (optional) and a null modem adapter
One RS-232 cable (9-pin female/25-pin male) to connect the PG/PC to the local modem. Some modems require a 9-pin female/9-pin male connector; check your local modem connection.
One set of European or U.S. modems with 9.6 kbaud or 19.2 kbaud support
One STEP 7-Micro/WIN 32 version 3.x software package

This application tip gives a summary of modem support for STEP 7-Micro/WN 32 version 3.x. All predefined modems have been tested and verified using the European CTA 104 C T-Net phone line simulator and the U.S. Ring-It phone line simulator. Modem tests consisted of 10-bit or 11-bit data formats at the rates of 9.6 kbaud and 19.2 kbaud, using the isolated 5 switch PC/PPI cable. The 5-switch cable eliminates the need for a null modem adapter between the PC/PPI cable and the remote modem. Use of a 4-switch PC/PPI cable requires a null modem adapter and the 11-bit data format strings.

Isolated 5-Switch PC/PPI Cable Settings:

Baud Rates	Switch 1	Switch 2	Switch 3	Switch 4	Switch 5
9.6 kbps (10 bit)	0	1	0	1	1
9.6 kbps (11 bit)	0	1	0	0	1
19.2 kbps (10 bit)	0	0	1	1	1
19.2 kbps (11 bit)	0	0	1	0	1

Initial Setup

Determine the baud rate for the remote CPU. The baud rate should be set at either 9.6 kbaud or 19.2 kbaud.
Set the first three DIP switches on the PC/PPI cable to the same CPU baud rate.
Determine the modem data format string for 10-bit or 11-bit protocol. Most modems default to the standard 10- bit parity. Some modems support both formats.
Set the number four DIP switch on the PC/PPI cable to the same modem data format string. 1 (up) equals 10-bit parity and 0 (down) equals 11-bit parity.
Set the number five DIP switch on the PC/PPI cable for data terminal equipment (DTE). This switch is always at 1 (up) for modem communications.

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 the steps outlined in the STEP 7-Micro/WIN online help under "Communicating With Modems."

For remote modem setup, connect the RS-232 serial cable from your computer directly to the remote modem. Using STEP 7-Micro/WIN 32, configure the remote modem by means of the Program/Test button in the modem Configure dialog box. Disconnect the RS-232 serial cable from the remote modem and connect the 5-switch PC/PPI cable to the remote modem and to the CPU. Plug the remote telephone line (RJ-11) into the remote modem.
For local modem setup, connect the RS-232 serial cable from your computer directly to the local modem. Using STEP 7-Micro/WIN 32, configure the local modem by means of the Program/Test button in the modem Configure dialog box. Plug the local telephone line (RJ-11) into the local modem.

Enter the telephone number in the Dial dialog box. Click on the Connect button to establish a modem connection.

NOTE:

It is recommended that the mode switch position of the remote CPU be placed in the RUN position so that the CPU will power up in RUN mode. However, some of the older CPUs (CPU 212 and CPU 214 prior to the February 1999 firmware 1.10 upgrade) do not support download from STEP 7-Micro/WIN while the mode switch is in the RUN position.

Description of AT Commands Used by STEP 7-Micro/WIN 32

Different modem types may accept different AT commands for the same modem operations. The modem functions listed below represent all the AT commands used by all the predefined modems supported by STEP 7-Micro/WIN 3.x. Some modem commands combine baud rates and parity settings together. For example, s23=58 is 9.6 kbaud, but s23=58 also contains the 11-bit parity setting. Consult your modem manual for your specific modem AT commands.

ATDT	Dial tone mode
ATH0	Hang up
E0	Echo on
E1	Echo off
F0	Modem is configured for autobaud operation.
Q0	No parity
Q2	Turn off answer mode responses and echo.
S0=1	Turn on auto answer (answer on first ring).
X0	Does not look for dial tone or busy signal.
X3	If dial tone detection is enforced and dial tone is not detected, NO CARRIER is reported.
^M	Carriage return
&C1	DCD follows the state of the carrier.
&D0	Modem ignores DTR signal.
&E3, &K0	Disable DTE/DCE flow control.
&E12	Disable pacing.
&F, &F0	Load factory defaults from modem ROM.
&Q6, &E0, \N0	Turn off error correction.
&W0	Store current settings in modem RAM. Load them on power up instead of loading the factory defaults from ROM.
&Y0	Modem uses profile 0 on power up.
$EB0	10-bit mode enabled (standard).
$EB1	11-bit mode enabled.
%E5	OK response to +++AT <CR>.
\C0	No data buffering in transaction phase
\Q0	No handshake

Baud rate commands (9.6 kbaud):
	*W=9600	+MS=11,1,	+MS=12,1,
	+MS=56,0,	%B9600	$SB9600
	$MB9600	s23=42	S23=58

Baud rate commands (19.2 kbaud):
	*W=19200	+MS=11,1,	+MS=12,1,
	+MS=56,0,	%B19200	$SB19200
	$MB19200	s23=44	s23=60

Parity settings (10-bit)
	,8,N,1	$EB0	s23=42
	s23=44	s28=70	Q0

Parity settings (11-bit)
	,8,E,1	$EB1	s23=58
	s23=60

Radio Modems

The MDR100A-R3 radio modem is a full duplex modem that can be used to form networks with one master and one or more slaves. The network may include repeaters or be operated without repeaters depending upon the area (distance to be covered). While the radio modem may be used in other configurations, this description is restricted to the case where a single master communicates with one or more S7-200 PLCs which act as slaves. The master may be STEP 7–Micro/WIN setup as a single PPI master or an S7-200 PLC operating in Freeport mode. Each S7-200 slave must have a unique address assignment.

In this configuration, one MDR100A-R3 radio modem must be configured as a Point-to-Point Master. All other MDR100A-R3 radio modems used in this configuration must be configured as Point-to-Point Slaves. While it is possible to use repeaters, this description is restricted to the case where repeaters are not used. In order to form a functional network, the radio modem configured as a Point-to-Point Master must be set up with the call number of each slave modem on its call list. Correspondingly, each slave must have the call number of the master on its call list.

Radio Modem Type

Model number		MDR100A-R3
Manufacturer		Black Box Corporation 1000 Park Drive Lawrence, PA 15055-1018 USA
Phone number		01 (724) 746-5500
Web site		www.blackbox.com
Frequency		902 to 928MHz (Spread Spectrum using frequency hopping methods)
Range		20 miles with external antenna (line of sight); w/o repeaters
Output power		0.1 to 1W, selectable
RS232 baud rates		1200, 2400, 4800, 9600, 19.2 kbaud, 38.4 kbaud, 57.6 kbaud, 76.8 kbaud, 115.2 kbaud
Data size		7 or 8 bits
Parity		Odd, Even, or None

Configuring the Radio Modem

Each modem in the network must be set to the same baud rate, number of data bits and parity selection. For this example the radio modems will be configured for operation in the network shown in the figure below.

Note: While radio modem documentation indicates that communication with multiple Point-to-Point Slaves is possible, the only configuration tested was with one Point-to-Point Master talking to one Point-to-Point Slave.

Before this network configuration can be put into operation, each radio modem must be configured according to the function that it must perform in the network. In this network there is only one radio modem that must be configured as a Point-to-Point Master and one or more radio modems that must be configured as a Point-to-Point Slave. In order to configure the radio modems, a terminal emulator running on a PC must be used.

For this example, Hyper Terminal emulator will be used. This is a standard accessory that is provided by the Windows operating system. Hyper Terminal can be invoked by clicking on the Windows 95 Start box. Doing this brings up a selection window. Slide the cursor to the Programs icon and then to the Accessories icon. Under the Accessories icon click on Hyper Terminal.

This opens the Hyper Terminal window which contains several icons. Double-click on the Hypertrm.exe icon which opens a Connection Description dialog box. Your cursor is automatically placed in the Name field. Enter a name like MDR100A-R3 and select the icon for this connection and click OK. This brings up the Phone Number dialog box. The MDR100A-R3 modems do not have a phone number associated with them, so leave the country code, area code, and phone number fields blank. In the Connect Using field, choose a direct connection with whichever communication port you wish to use and click OK. The next dialog box is for the Port Settings.

Enter the following settings:

Bits per second		19,200
Data bits		8
Parity		None
Stop bits		1
Flow control		None

Then click OK to complete the Hyper Terminal setup for the MDR100A-R3 modem.

Note: In order for these changes to take effect, you may have to disconnect Hyper Terminal and then re-connect.

Hyper Terminal is now ready to use for configuring the radio modem. Using a straight through RS232 cable, connect the radio modem to the PC which is running Hyper Terminal. With the radio modem connected to Hyper Terminal and powered up, use a paper clip or other suitable object to depress the setup button on the radio modem. The setup button is not identified in any way on the radio modem, but access to the setup button is provided through a tiny hole in the case on the side opposite the RS232 connector.

Depressing the setup button on the radio modem places the modem in setup mode. This mode is indicated by illuminating the P and C (Power and Carrier) LEDs and by the modem sending the setup menu to Hyper Terminal. Make the following choices to configure the radio modem as a Point-to-Point Master running at 9600 baud.

Main Menu
Press 0 to set the operating mode.
Set Modem Mode Menu
Press 0 to set the operating mode to Point-to-Point Master.
Press the ESC key to return to the Main Menu.
Press 1 to set the baud rate.
Press 6 to select 9600 baud.
Press A to select Data and Parity.
Press 4 for 8 data bits, Even Parity and 1 Stop bit. Press the ESC key to return to the Main Menu.
Press 2 to edit the Call Book
Press 0 to enter the call number of the first radio modem slave.
Press ESC if repeaters are not being used.
Press 1 to enter the call number of the second radio modem slave.
Press ESC if repeaters are not being used.
Repeat as required to enter the call number of up to 10 radio modem slaves. Each radio modem's call number is printed on a label just beneath the RS232 port of each modem.
Press C to change the call number to use.
Press A to call all stations.
Press the ESC key to return to the Main Menu.
Press 3 to edit the radio transmission characteristics.
Press 5 to modify the transmitter output power.
Enter the desired output power level for the transmitter (0 to 9 with 9 being maximum power). Press the ESC key to return to the Main Menu.
Press the ESC key to exit setup mode.

This exits the setup mode for the radio modem master. Disconnect the master from Hyper Terminal and then set up each radio modem slave in turn.

Connect the first slave to Hyper Terminal using the same cable as was used to configure the radio modem master and depress the setup button on the radio modem. Make the following choices to configure the radio modem as a Point-to-Point Slave running at 9600 baud:

Main Menu
Press 0 to set the operating mode.

Set Modem Mode Menu
Press 1 to set the operating mode to Point-to-Point Slave.
Press the ESC key to return to the Main Menu.

Press 1 to set the baud rate.
Press 6 to select 9600 baud.
Press A to select Data and Parity.
Press 4 for 8 data bits, Even Parity, and 1 Stop bit.
Press the ESC key to return to the Main Menu.

Press 2 to edit the Call Book.
Press 0 to enter the call number of the radio modem master.
Press ESC if repeaters are not being used.
Press C to change the call number to use.
Press A to call all stations.
Press the ESC key to return to the Main Menu.

Press 3 to edit the radio transmission characteristics.
Press 5 to modify the transmitter output power.
Enter the desired output power level for the transmitter (0 to 9 with 9 being maximum power).
Press the ESC key to return to the Main Menu.

Press the ESC key to exit setup mode.

Disconnect the radio modem slave and repeat the above procedure for each radio modem slave.

Connecting the Network

Once all radio modems have been properly configured, the radio modem master will establish communication with the slaves. When communication has been established, the C (carrier) LED on the radio modem will illuminate. Correspondingly, when a radio modem slave receives a transmission from the radio modem master, it will illuminate its C LED as an indication. The radio modems do not need to be connected to any other equipment for the carrier LED to illuminate.

With the radio modems configured and communication established, connect the radio modem master to the PC as shown in the diagram of the network and start STEP 7–Micro/WIN. Then connect a single S7-200 with a station address of 2 to a radio modem slave using the Isolated PC/PPI cable. Be sure to set the switches on the Isolated PC/PPI cable as shown in the figure above.

In Case of Difficulty

If you cannot establish communication from STEP 7–Micro/WIN to the S7-200 using this procedure, first connect STEP 7–Micro/WIN directly to the S7-200 and make sure that there are no problems before inserting the radio modems. Note that you will need to change Switch 5 to 0 (Down) for a direct connection to the S7-200.

Next, make sure that the radio modem master is in communication with the radio modem slave by powering down both the radio modem master and the slave. Power the radio modem slave up first and make sure that the P(ower) LED is illuminated, then power up the radio modem master. The P(ower) and C(arrier) LEDs should illuminate on both the master and the slave shortly after powering up the master. This indicates that communication has been established between the radio modems.

If these steps are completed successfully and communication between STEP 7–Micro/WIN and the S7-200 cannot be established over the radio modems, check to make sure that the communication setup of STEP 7–Micro/WIN and the S7-200 match that of the radio modems. In this case make sure that both STEP 7–Micro/WIN and the S7-200 are set to 9600 baud.

If communication still cannot be established, re-check the setup of the radio modems.

Modem Troubleshooting Guide

Problem	Possible Causes	Solution
Receive failure message when trying to program the predefined local or remote modem for STEP 7–Micro/WIN.	Wrong modem type selected. Wrong communication mode selected (10-bit or 11-bit). Cable not connected to modem. Using wrong PG/PC comm port. Remote modem is not directly connected to the PC/PC for programming	Confirm correct local modem type. Some modems are defined twice with 10-bit or 11-bit parity settings. In the modem setup dialog box, the parity mode must also match the modem parity selected. Check cable connection to modem. Check the comm port selection in the PC/PC interface dialog box Click the Properties button and verify the comm port selection in the local connection tab. Both modems must be configured with a direct point-to-point cable connection from the PC/PC to the modem.
Receive failure message when trying to program a user-defined local or remote modem.	Same possible causes as the predefined modems above. User AT commands may be wrong. Remote modem is not directly connected to the PG/PC for programming.	When defining the AT command strings for a new modem, start with the factory defaults. Follow each additional AT command one at a time until you receive an error message. The last AT command used is the problem. In general, the following settings should be used for new modems when using STEP 7–Micro/WIN: - disable flow control - ignore DTR signal - turn off error correction - if modem supports both parities, specify one - turn off answer mode responses and echo - use the correct baud rate command The remote modem must be configured with a direct point-to-point cable connection from the PG/PC to the remote modem. In general, use the same modem settings for both user-defined modems. However, add the following AT commands for the remote modem: - answer on the first ring - store the current settings in the modem RAM
Modems do not connect. Receive "Error establishing modem connection."	Local modem not configured correctly with the remote modem. Remote modem not configured correctly with the local modem. Local and remote modems are not compatible with each other. Baud rate not set correctly. RJ11 phone line is not plugged in the right modem jack. No remote modem at the other end. Timeout connect setting needs adjusting. Incorrect telephone number Incorrect dial tone Busy signal	STEP 7–Micro/WIN does not store the local modem's AT commands in the modem's RAM. If the local modem has been power cycled, you may lose your user-defined AT commands. STEP 7–Micro/WIN automatically tries to resend the AT commands when trying to connect to the modem, but only at the current baud rate and parity. If this fails, try to reconfigure the local modem by using the "Program/Test" button in the modem setup dialog box. This automatically tries multiple baud rate and parity settings. Also ensure STEP 7–Micro/WIN and both local and remote modems are set at the same parity format. The remote modem parameters must be stored in the modem's RAM in order to keep them on power cycles. If possible, use the same type of modems for local and remote modem communications. STEP 7–Micro/WIN, the 5-switch PC/PPI cable, and both modems must be set at the same baud rate. Some modems have two RJ11 jacks, one labeled "Line" and the other "Phone." Make sure the telephone line from the wall is plugged into the "Line" jack, and the telephone line from the phone is plugged into the "Phone" jack. Verify the remote modem at the other end by using a third-party communications package such as HyperTerminal. If you can make a connection, STEP 7–Micro/WIN should also make the same connection. If not, the modems may not be configured correctly. In the configure dialog for the local modem, increase the timeout setting. Use increments of 15 seconds. Verify the correct telephone number. Some telephone numbers require a pause (,) between numbers. Consult your modem manual for specific telephone entries. Make sure you are using the correct dial tone AT command for calling (ATDT for tone dial). Wait a few minutes and try calling again.

Important Notes for Modem Support

STEP 7-Micro/WIN 32 version 3.x will support a FIND operation for the 11-bit modems.
STEP 7-Micro/WIN 32 version 3.x will not support a FIND operation for the 10-bit modems.
STEP 7-Micro/WIN 32 version 3.x will not support internal modems that use the PCI card or ISA card slot.
You may also program the remote modem by using a third party communications package such as HyperTerminal that comes standard with Windows. However, it is recommended that you use the predefined AT commands as specified by the STEP 7-Micro/WIN 32 modem configuration setup. These modem parameters are especially designed to work with Siemens remote CPU communications. If your modem type is not listed in STEP 7-Micro/WIN 32, use similar modem settings for your specific modem type.
There is an extensive online help that provides detailed instructions for modem communications. Search under "modems." The S7-200 Programmable Controller System Manual also provides additional information.