Configuring SIMOREG DC-Master DriveMonitor Serial Connection

Overview

The SIMOREG DC-Master 6RA70 family of converters uses an optional SST1 serial interface board (designated G-SST1 in the parameter tree) for commissioning and parameterization with Siemens DriveMonitor software. Establishing a reliable PC-to-drive link requires three coordinated layers: (1) the SST1 hardware option correctly installed in the drive electronics box, (2) a correctly wired RS-232 cable between the SST1 9-pin D-sub connector and the PC COM port, and (3) matching parameter values on both the converter side (G-SST1 parameters P780 through P786) and the DriveMonitor online interface. When the original Siemens serial cable is unavailable and a replacement is fabricated from the service manual drawing, the most common commissioning failures are wiring errors, parameter mismatches, and COM port misconfiguration. The factory-default parameter set documented below is the safest starting point when a known-good cable is not available.

Interface Identification

The serial interface used for USS protocol communication is the SST1 communications board, referenced in the converter parameter tree as the G-SST1 function group. The board plugs into a dedicated option slot in the SIMOREG electronics box and exposes a 9-pin male D-sub connector on its front panel, labeled X500, for point-to-point RS-232 connection to a PC running DriveMonitor.

Before configuring any parameters, confirm that the SST1 board is properly seated and recognized by the converter. From the SIMOREG operator panel (PMU), navigate to the G-SST1 parameter group. If the parameters are not visible in the menu tree, the SST1 board is either not installed, not fully seated, or not initialized by the converter firmware.

The installed SIMOREG software version is read from the following display parameters:

• r060 – Software version of the SIMOREG DC-MASTER
• r065 – Software version detail

These two parameters must be recorded before any firmware update or DriveMonitor upgrade. The latest SIMOREG DC-Master firmware updates and release notes are published at the official Siemens Industry Online Support portal. Refer to the SIMOREG DC-Master support documentation for version-specific release notes and the DriveMonitor compatibility matrix.

Cable Requirements and Pinout

When the original Siemens serial cable is unavailable, a replacement can be fabricated following the service manual wiring diagram. The RS-232 link between the SST1 X500 connector and the PC COM port requires a minimum three-wire configuration: transmit data, receive data, and signal ground. Verify the fabricated cable with a multimeter against the service manual drawing before powering the drive. Pay particular attention to the TXD/RXD crossover, the shield-to-ground bond (bonded only at one end, typically the PC side), and that no conductor is shorted to an adjacent pin at either D-sub backshell.

Typical SST1 X500 (9-pin male) to PC DB-9 (9-pin female) null-modem wiring used for SIMOREG USS point-to-point:

Pins not listed should remain unconnected on both ends. Hardware handshaking lines (RTS, CTS, DTR, DSR, DCD, RI) are not used in USS point-to-point mode and must not be cross-linked; cross-linking handshaking lines is a common fabrication error that prevents reliable communication even when the data and ground lines are correct.

G-SST1 Parameter Configuration

When the converter leaves the factory, or after a parameter reset to defaults, the G-SST1 parameter group must be written with the values required for USS protocol operation on the SST1 channel. The following table lists the parameters and values for a single-drive, point-to-point commissioning link to a PC running DriveMonitor. These are the values documented in the service manual as the factory-typical starting point when the converter has not been previously integrated into a USS multi-drop network.

PKW (Parameter-Kanal-Werte / parameter channel values) carries parameter read and write transactions between the master and the converter. PZD (Prozess-Daten / process data) carries the real-time control words, setpoints, status words, and actual values. A value of 127 for P782 reserves the maximum PKW word count and forces a fixed-length telegram; this configuration simplifies parameter browsing from DriveMonitor at the cost of slightly higher bus utilization but is the documented service-manual default for commissioning links.

The PZD words used in this configuration are typically the SIMOREG control word 1 (PZD1 from master) and the main setpoint (PZD2 from master), with the SIMOREG status word 1 (PZD1 to master) and the main actual value (PZD2 to master) returned in the response telegram. The exact mapping depends on P794 and P795 in the G-SST1 group; consult the service manual for the firmware revision installed.

DriveMonitor Software Configuration

DriveMonitor is the Siemens commissioning tool for the SIMOREG DC-Master drive family. Version 5.4 SP2 (or later service packs published on the Siemens support portal) provides the online interface required for serial communication. After installing DriveMonitor on the PC and connecting the fabricated serial cable, configure the online interface using the following menu path and values.

Open the menu Tools → Online Settings → Interface. The Interface dialog allows selection of the PC COM port and the protocol parameters. Enter the following values:

• PC COM port: the port number Windows assigns to the USB-to-serial adapter or native RS-232 port
• Baud rate: 9600 bit/s (matches G-SST1 P783 = 6)
• Data bits: 8
• Parity: none
• Stop bits: 1
• Flow control: none (no RTS/CTS hardware handshake, no XON/XOFF software handshake)
• USS node address: 0 (must match G-SST1 P786)

Click OK to commit the online settings. DriveMonitor retains these settings in the user profile for subsequent sessions but does not re-verify them on every launch; an operator changing the COM port assignment in Windows Device Manager will silently break the next online attempt unless DriveMonitor online settings are also updated.

COM Port Settings

The Windows COM port configuration must match the DriveMonitor settings exactly. A mismatched baud rate, parity, or flow control is the single most common cause of failed connections when the cable wiring itself is correct.

To verify the COM port assignment in Windows: open Device Manager → Ports (COM & LPT) and identify which physical COM port number Windows has assigned to the USB-to-serial adapter (if used) or the native RS-232 port. Many USB-to-serial adapters default to COM3, COM4, or higher; if DriveMonitor is configured for COM1 but the adapter is on COM7, the online connection will time out without any explicit error message.

Step-by-Step Commissioning Procedure

The following procedure establishes a verified serial link between DriveMonitor and the SIMOREG DC-Master. Execute the steps in order and do not skip the verification checkpoints between phases.

1. Confirm SST1 board installation. Power up the converter electronics section and navigate the PMU to the G-SST1 parameter group. If the parameters are not visible, the SST1 board is either not installed, not seated correctly, or not recognized by the firmware.
2. Record current software version. Read parameters r060 and r065 from the PMU and record the values. These are required if a firmware or DriveMonitor upgrade becomes necessary.
3. Write G-SST1 parameters to USS defaults. Set P780 = 2, P786 = 0, P783 = 6, P782 = 127, P781 = 2 and save to the converter's non-volatile memory.
4. Cycle converter control voltage. Power the electronics section off and on so the new SST1 parameters take effect. Some firmware revisions require a full power cycle before the new serial parameters are accepted by the SST1 board.
5. Connect the fabricated serial cable between the SST1 X500 connector and the PC COM port. Hand-tighten the connector screws on both D-subs.
6. Verify the COM port assignment in Windows Device Manager and note the COM port number.
7. Configure the COM port to 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control.
8. Launch DriveMonitor 5.4 SP2 (or later service pack).
9. Open Tools → Online Settings → Interface and enter the COM port, 9600 baud, 8/N/1, no flow control, USS address 0.
10. Initiate the online connection from the DriveMonitor menu (typically Online → Connect or the equivalent toolbar button). DriveMonitor will issue USS request telegrams to the drive.
11. Read parameter r060 from the drive via DriveMonitor. The returned value confirms end-to-end communication and validates the parameter read path.
12. Read parameter P780 from the drive to confirm the parameter write path is also functional. The value should be 2.

Verification and Diagnostics

Successful online connection is confirmed when DriveMonitor displays the drive's parameter tree and live process values without timeout errors and when parameter read/write operations complete within the expected response time. Use the following diagnostic checks to isolate persistent issues:

• USS response timeout: Indicates no response from the drive. Verify the cable TXD/RXD crossover, the COM port number assignment, the baud rate setting, and that the converter is powered, not in a fault state, and not in the middle of a firmware upgrade.
• Parity or framing errors: Indicate baud rate or parity mismatch between DriveMonitor and G-SST1. Double-check P783 against the DriveMonitor online settings, and verify that no flow control is enabled on either side.
• Wrong node address: If P786 is non-zero, DriveMonitor must be configured to poll that exact USS address. DriveMonitor's address field is a free numeric entry; an off-by-one error (1 versus 0) is a frequent commissioning mistake.
• Drive in fault with no control voltage: The SST1 interface may not respond when the converter is in a state that disables the option slot. Clear all drive faults and verify that the converter is in a ready state before expecting a serial response.
• Intermittent connection: Usually indicates a loose D-sub connector, a broken solder joint in the fabricated cable, or a USB-to-serial adapter that loses synchronization at higher bus activity. Reseat both connectors and inspect cable ends.

Troubleshooting Matrix

Software Version Identification and Upgrade Path

Before downloading a different DriveMonitor service pack or converter firmware update, identify the currently installed SIMOREG software version from parameters r060 and r065. This step prevents installing firmware that is incompatible with the installed hardware option boards or with the converter's electronics box revision. The two read-only parameters together identify the firmware major version, minor version, and service pack level.

The latest SIMOREG DC-Master software version, its release notes, and the matching DriveMonitor service pack are published on the Siemens Industry Online Support portal. Refer to the SIMOREG DC-Master support documentation for the current firmware file, mandatory compatibility notes with DriveMonitor versions, and the upgrade procedure for the SST1 option board.

When upgrading, always:

1. Record r060 and r065 before the upgrade.
2. Back up the complete parameter set using DriveMonitor's upload function.
3. Verify that the new DriveMonitor version supports the existing G-SST1 parameters without re-mapping.
4. After the upgrade, verify the serial link by reading r060 back via the online connection before assuming the upgrade succeeded.

Field-Commissioning Notes

Several practical issues surface during field commissioning that are not apparent from the parameter tables alone. The following field-proven notes apply when a fabricated cable replaces the original Siemens serial cable on a SIMOREG 6RA70 site.

Shielding and ground loops: Bond the cable shield to the PC-side D-sub backshell only. Do not bond the shield at the SST1 end. A double-bonded shield creates a ground loop that injects common-mode noise into the RS-232 signal pair, causing intermittent timeout errors at long cable runs (greater than 3 m).

Cable length: The RS-232 standard limits cable length to approximately 15 m at 9600 bit/s. For longer distances, use an RS-232 to RS-422/RS-485 converter on the PC side and configure the SST1 board's RS-485 mode (if the SST1 variant supports it), or move to a PROFIBUS SST1 board and use a PROFIBUS-to-USB adapter on the PC.

Drive fault state: A SIMOREG in a hard fault state (for example, an overcurrent or field loss fault) may still respond to USS parameter reads but will reject parameter writes that would change operating setpoints. Clear all faults before attempting to write parameters from DriveMonitor.

Multiple SST1 boards: If the converter has both an SST1 and a PROFIBUS or other communications board installed, ensure that only one board is configured with P780 in its respective parameter group, otherwise bus contention will corrupt the telegrams.

FAQ