RS232 Communications Overview

In some cases, more recent PG/PC devices no longer have an RS232 interface but only USB interfaces. In order to still be able to address Siemens standard inverters using these PG/PC (e.g. PC COM-Port (USS protocol)), we recommend that USB<->RS232 adapters are used.

The following adapters have been tested:

• Roline USB to serial 9-pin converter, Order No. 12.02.1086 (www.roline.com)
• Conrad USB-modem adapter, Order No. 98 24 17 (www.conrad.de)
• SITECOM USB Serial cable CN-104 – USB to serial (www.sitecom.com)
  

COM port number
When a USB<->RS232 adapter is first inserted into a USB port, then the operating system assigns it a new COM port number that was previously not used.

This COM port number depends on the number of USB interfaces that the computer has as well as the devices that were previously used at this computer. The COM port number of the USB<->RS232 adapter must be known in order to select the correct COM port in STARTER or Drive Monitor to establish the online connection.

This COM port number can be checked in the Device Manager and/or modified as required (refer to Fig. 1-1 right). In this example, the COM port number COM7 is used for the USB<->RS232 adapter ATEN USB to Serial Bridge.

Different behavior of STARTER and Drive Monitor when selecting the COM port number.

The different behavior of the STARTER and Drive Monitor tools - regarding the selection of the COM port number - is discussed in the subsequent text.

Behavior in STARTER

New COM port numbers are automatically added to the selection list in the "Set PG/PC interface…" under the tab "Interface" and can be selected from there. Here, there are no restrictions regarding the COM port number. Note: It should be noted that in the "Set PG/PC interface…" for "PC COM-Port (USS)" under tab "RS485" automatic operation must be selected. Otherwise online operation with a USB adapter at RS232 is not possible.

Behavior in Drive Monitor

In Drive Monitor it is only possible to select either COM1 - COM4. The selection list is not supplemented by active and/or existing interfaces. The four selection possibilities are fixed. The COM port number of the USB<->RS232 adapter should therefore be changed so that it lies between 1 - 4.

Only then is it possible to select the correct interface in the Drive Monitor and establish an online connection. When initialized by the operating system, if the USB<->RS232 adapter is assigned e.g. a COM port number 5 or higher then the COM port number must be changed (< 5).

To do this, select your USB<->RS232 adapter in the device manager under "Ports (COM & LPT)" by double clicking on it. The "Properties" window of the USB<->RS232 adapter opens. Here, open the tab "Port Settings" (refer to Fig. 1-2 right).

Keep the default settings of all of the parameters and press the "Advanced…" button. The "Advanced Settings" window for the COM port is displayed. Select the COM port number from the list that opens between 1 - 4 (refer to Fig. 1-3 below).

It is possible that all COM port numbers between 1 and 4 are occupied. In this case, select one that you are not using and exit the window with "OK". A message is displayed that this COM port is already being used by another device; acknowledge this with "Yes"

Note: Please note that in the "ONLINE Settings" for bus operation via RS485 the automatic mode must be selected under the "Interface" tab. Otherwise, online operation with a USB adapter at RS232 is not possible.