Configuring CPU 314-2PN/DP, TP 177A, AUMATIC on PROFIBUS DP

System Overview

This technical reference describes the integration of a Siemens SIMATIC S7-300 CPU 314-2PN/DP acting as a PROFIBUS DP Class 1 master, a SIMATIC TP 177A operator panel acting as a DP slave, and an AUMA AUMATIC ACExC 01.2 actuator controller with PROFIBUS DP-V1 interface. The three devices share a single RS-485 PROFIBUS segment connected to the CPU's MPI/DP port (X1). The TP 177A and AUMATIC exchange process data with the CPU entirely through the PROFIBUS DP cyclic I/O mechanism; no additional SFCs/SFBs are required in the STEP 7 user program because the DP master firmware writes the inputs and outputs directly into the process image of the CPU.

Architecturally, the CPU 314-2PN/DP (order number 6ES7314-2EH14-0AB0) has only one RS-485 interface at front connector X1. This port can be parameterized in STEP 7 HW Config as either MPI or PROFIBUS DP, but not both at the same time. The PROFINET port at X2 (two-port switch) cannot transport PROFIBUS DP frames, so all DP slaves must reside on the same RS-485 segment that is wired to X1. The AUMATIC ACExC 01.2 is supplied as the actuator control electronics for AUMA SA/SAR/SAEx/SAREx multi-turn and part-turn actuators; the "non-intrusive" variant means the setting and control elements are accessible without opening the Ex enclosure, which is a relevant constraint for hazardous-area installations.

Hardware Components and Part Numbers

The following table lists the components used in a typical configuration. The procedure also applies to the standard AC 01.2 variant because both share the same PROFIBUS DP-V1 communication module.

The CPU 314-2PN/DP has 192 KB of code work memory and 64 KB of data work memory. Bit instructions execute in 60 ns and floating-point operations in roughly 240 ns. The integrated PROFINET interface supports up to 8 PROFINET IO devices with a minimum update time of 1 ms. The MPI/DP port supports baud rates from 9.6 kbps to 12 Mbps. The CPU can act as a DP master (with up to 32 DP slaves) or as a DP slave, but in this configuration it must be parameterized as a DP master.

The TP 177A 6AV6642-0BA01-1AX1 supports PROFIBUS DP at up to 1.5 Mbps. For higher baud rates (3, 6, 12 Mbps), the TP 177A DP with order number 6AV6642-0BC01-1AX1 must be used; this is the relevant speed limit for the network shown here, which is why the discussion example uses 1.5 Mbps. The TP 177A is configured with WinCC Flexible 2008 SP3 or later.

PROFIBUS DP Cable, Connectors, and Topology

PROFIBUS DP uses an RS-485 physical layer defined in IEC 61158-2 / EN 50170. The bus is a linear, terminated line with a defined number of segments. Every segment must be terminated at both physical ends with a 220 Ω resistor in series with a 390 Ω pull-up to +5 V (pin 6) and a 390 Ω pull-down to DGND (pin 5) on each line. Active terminating connectors (Siemens 6ES7972-0DA00-0AA0) provide an electronically switched terminator that can be left permanently installed in some networks.

The maximum segment length depends on the configured baud rate. The following table summarizes the limits defined by the PROFIBUS standard:

For this configuration, the entire DP bus runs at 1.5 Mbps because the TP 177A is the limiting device. The CPU 314-2PN/DP and the AUMATIC both support 1.5 Mbps without problems, so the bus baud rate is set in HW Config to 1.5 Mbps. The AUMATIC is set to "automatic baud rate detection" because the actuator module auto-detects the line baud rate on power-up.

The Siemens PROFIBUS connector 6ES7972-0BB12-0XA0 has two cable entries: a "cable from previous station" port (A1, A2) and a "cable to next station" port (B1, B2). The connector pinout is defined as follows:

The A and B letters on a Siemens 9-pin D-sub connector refer to the two cable entries:

• A1 = Pin 8 (A line) of incoming cable
• A2 = Pin 3 (B line) of incoming cable
• B1 = Pin 8 (A line) of outgoing cable
• B2 = Pin 3 (B line) of outgoing cable

Wiring between two stations must be straight: A1 of the left connector goes to B1 of the right connector, and A2 of the left connector goes to B2 of the right connector. Crossing the lines (A1 to A1 and A2 to A2) is the most common wiring error and causes a bus fault that the CPU reports as a station failure with diagnostic identifier 0x0E (hardware fault of the bus interface).

CPU 314-2PN/DP PROFIBUS Master Configuration

The MPI/DP port (X1) of the CPU 314-2PN/DP must be parameterized as PROFIBUS DP master with a network address. In STEP 7 HW Config, open the CPU properties and select the X1 interface, then set the following values:

The CPU must remain in the middle of the bus. With only three stations, the correct bus topology is:

• TP 177A at one physical end of the cable, terminator ON
• CPU 314-2PN/DP in the middle, terminator OFF
• AUMATIC at the other physical end of the cable, terminator ON

Because the CPU is in the middle, both cable entries (A1/A2 and B1/B2) of the CPU connector are used. The terminating resistor of the CPU connector must be switched OFF. The terminator of the AUMATIC and the terminator of the TP 177A must be switched ON. With only two physical terminators, the bus is properly terminated and the DC load on each line is the parallel combination of 220 Ω at each end, which gives the correct 110 Ω nominal line impedance.

The PROFIBUS bus timing parameters that can be set in HW Config (in the Properties dialog of the master) are:

Use the default values for 1.5 Mbps. Do not lower Tslot below the default, because the AUMATIC and TP 177A both need a non-trivial station delay to respond.

TP 177A PROFIBUS Slave Configuration

The TP 177A in this configuration operates as a DP slave at address 2 with a fixed baud rate of 1.5 Mbps. WinCC Flexible 2008 is used to create the panel project. The following parameters are set in the TP 177A device properties within WinCC Flexible:

The TP 177A does not require any hardware configuration on the connector for this configuration. The default connector shipped with the panel has a terminating resistor that should be left ON because the panel is at one physical end of the bus.

To compile and download the panel project, connect the programming PG to the TP 177A via the same PROFIBUS subnet (or via PROFINET) and use WinCC Flexible Transfer. Verify that the "Download" dialog shows the correct target device and the correct connection parameters before transferring the project to the panel. The PG/PC interface must be set to "PROFIBUS DP" and the correct baud rate.

The panel project must declare the same input and output byte offsets as the STEP 7 HW Config. For a 2-byte output and 4-byte input AUMATIC configuration, the typical setting in WinCC Flexible is:

AUMATIC ACExC 01.2 PROFIBUS DP-V1 Configuration

The AUMATIC ACExC 01.2 is the actuator control electronics for AUMA SA/SAR/SAEx/SAREx multi-turn and part-turn actuators. The PROFIBUS DP-V1 communication module is a plug-in card on the AUMATIC, located under the top cover of the housing. The module has a rotary address selector (0 to 125, usually set with two BCD-coded rotary switches) and a baud rate selector (or automatic detection).

The following parameters must be set on the AUMATIC PROFIBUS module:

For the "non-intrusive" variant of the ACExC 01.2, the setting elements (rotary address switches, terminator switch, baud rate switch) are accessible through a window in the housing cover, so the enclosure does not need to be opened. This is required for use in hazardous areas where opening the enclosure under power is not allowed.

The AUMATIC provides the following I/O by default on PROFIBUS DP-V1:

• Process output (master → AUMATIC, 2 bytes): Remote control word with bits for OPEN, CLOSE, STOP, EMERGENCY, and operating mode selection (local / remote, etc.).
• Process input (AUMATIC → master, 4 bytes): Status word with end position feedback (open, closed), running indication, fault summary, and warning summary.
• Acyclic parameters: Position, torque, and other diagnostic values accessible via DP-V1 read/write services (used by the AUMATIC service tool or by FDT/DTM).

The AUMATIC PROFIBUS module has two LEDs on the front of the unit: a green "BUS" LED (lit when the slave is in cyclic data exchange with the master) and a red "ERR" LED (lit on bus fault or address conflict). For hazardous-area installations, observe the device's ATEX/IECEx marking and ensure that the bus cable enters the housing through a certified cable gland.

STEP 7 HW Config: Integrating the AUMATIC GSD

To bring the AUMATIC into the STEP 7 project, install the AUMA GSD file. The GSD file is supplied with the AUMATIC PROFIBUS module (typically named AUMA0F1F.GSD or a later revision) and is also available on the AUMA support website. In STEP 7:

1. Close all open projects.
2. Open Options → Install GSD File and browse to the .GSD file and the matching .BMP icon file.
3. Confirm the installation. The AUMATIC appears in the HW catalog under PROFIBUS DP → Additional Field Devices → Actuators → AUMA Riester GmbH → AUMATIC.
4. Open the STEP 7 project, then drag the AUMATIC DP slave onto the PROFIBUS subnet (1.5 Mbps).
5. Set the AUMATIC address to 3.
6. Insert the desired DP-V1 slot modules into slots 0, 1, 2 etc. The default I/O configuration is "1 Word In / 2 Words Out" or similar, depending on the GSD revision. Verify the byte count matches the AUMATIC's actual cyclic data size.
7. Verify the configured I/O addresses in the Addresses tab. STEP 7 will assign input/output bytes (e.g. IB 0, QB 0) for the AUMATIC I/O. These addresses are part of the CPU's process image and can be read directly from the user program.
8. Compile and download the hardware configuration to the CPU.

The configured I/O addresses for the AUMATIC must match the tag addresses used in the TP 177A panel project. Use the same byte offset (e.g. 0) on both sides. If you change the slot configuration in HW Config, recompile the hardware configuration and re-download to the CPU before the panel will display the new layout correctly.

The PROFIBUS DP-V1 GSD file for the AUMATIC exposes the following slot modules commonly used in this application:

WinCC Flexible 2008: TP 177A Tag Configuration

To make the TP 177A display process data, configure tags in WinCC Flexible 2008. Use a PROFIBUS DP connection to the CPU and define the tag types as follows:

The default area pointer for the connection is "Area pointer 1" (data record 0x10 for cyclic data). The TP 177A reads its process data from the configured input area and writes its process data to the configured output area. The size of the data areas must match the configured I/O size of the AUMATIC; otherwise the panel will report a configuration error on transfer.

To verify the tag addressing, open the Connections dialog in WinCC Flexible, select the PROFIBUS connection, and click on Properties → Tags. Each tag must be assigned to a valid input or output byte. Use the Cross-reference tool (Ctrl+Alt+F) to find all places where a tag is used in screens, recipes, or scripts.

The connection is a true DP connection, so the TP 177A exchanges data with the master at the configured PROFIBUS update rate (typically a few milliseconds at 1.5 Mbps). The CPU's scan cycle does not affect the panel update rate; the panel sees the data as soon as the master writes it to the bus. This is much faster than a conventional MPI/PROFIBUS connection with WinCC area pointers at 8 Hz.

Commissioning Procedure

Commission the network in this order to localize any faults:

1. Visual inspection: Verify that all connectors are seated and the terminator switches are in the correct positions. A loose connector is the most common commissioning failure.
2. Continuity check: With the bus disconnected, use a multimeter to measure the resistance between pins 3 and 8 on each connector. The reading should be approximately 110 Ω (the parallel combination of the two 220 Ω terminating resistors) when the two end stations are powered, or 220 Ω when only one end is powered. An open circuit (OL) means both terminators are off or the cable is broken.
3. Power-up sequence: Apply power to the AUMATIC first, then to the TP 177A, then to the CPU. The AUMATIC and TP 177A need time to complete their internal initialization before the CPU begins the DP master polling.
4. LED check on the CPU: The "SF DP" LED should be off and the "BF DP" LED should be off. The CPU is in RUN with no DP fault. If BF DP is flashing, at least one slave is not responding. If BF DP is solid red, the bus is faulty.
5. LED check on the TP 177A: The "PROFIBUS DP" LED should be on or flashing green. The "COMM" LED should be on solid green once a connection is established with the master.
6. LED check on the AUMATIC: The PROFIBUS module has two LEDs: a "Bus" LED (green when the bus is healthy, red on fault) and a "Ready" LED (green when the module is ready for cyclic data exchange).
7. Online diagnostics in STEP 7: Open PLC → Monitor/Modify, enter the configured I/O address (e.g. IB 0 or QB 0) of the AUMATIC, and verify that the values update when the actuator moves.
8. Online diagnostics in WinCC Flexible: Open the TP 177A online connection and use the "Trace" function to log the values of selected tags over time. Verify that the values match the values seen in STEP 7.
9. Functional test: Issue an OPEN command from the panel and verify that the AUMATIC moves the actuator. Issue a CLOSE command. Issue an EMERGENCY stop. Verify that the status feedback is correct on the panel.
10. Diagnostic buffer check: In STEP 7, open PLC → Diagnostic Buffer and verify that no DP-related events are recorded (0x0131 station failure, 0x0157 bus fault, etc.).

If any LED is red, or if the values are stuck or zero, refer to the troubleshooting matrix in the next section.

Diagnostics, Buffer Entries, and Verification

The CPU 314-2PN/DP keeps a diagnostic buffer that records DP-related events. The relevant entries for a DP commissioning scenario are:

To read the diagnostic frame from a slave in STEP 7, open the slave online in HW Config, then PLC → DP Slave Diagnostics. The AUMATIC returns a vendor-specific diagnostic block that includes the actuator position, torque, and warning/fault bits. The TP 177A returns a standard DP-V1 diagnostic block that includes the slot-level status.

For the TP 177A, open the System → Messages view on the panel to see any HMI-level errors. Common panel messages include "Connection failed", "Address conflict", and "Tag not found".

For the AUMATIC, the local LCD on the actuator electronics shows the active fault and the last 20 events. Common AUMATIC diagnostic codes include:

Troubleshooting Matrix

The following matrix maps the most common symptoms to their root causes and the corrective action.

To distinguish between a cable fault and a configuration fault, temporarily disconnect the AUMATIC and check whether the TP 177A connects to the master. If the TP 177A connects, the bus is healthy and the fault is on the AUMATIC side. If the TP 177A does not connect, the fault is on the trunk or on the CPU configuration.

The CPU 314-2PN/DP does not automatically go to STOP on a DP slave failure as long as the relevant error OBs (OB82 for diagnostic interrupt, OB86 for rack/station failure) are loaded. If the CPU does go to STOP, the cause is usually a missing OB86. The OBs are in the STEP 7 standard library and can be inserted with a few clicks.

Field-Proven Tips and Long-Term Operation

Once the system is running, consider the following points for long-term reliability:

• Spare GSD on hand: Keep a copy of the AUMA GSD file (and a printout of the slot configuration) in the cabinet. A failing AUMATIC will likely be replaced with the same model; the spare must be commissioned with the same configuration.
• Spare PROFIBUS connectors: Keep at least two spare 6ES7972-0BB12-0XA0 connectors in stock. The contact pins of the connector can wear after 50–100 mating cycles, especially in vibrating environments.
• Document the byte map: Write the input and output byte addresses of the AUMATIC on the cabinet door, so that the next commissioning engineer can quickly verify the configuration.
• Watch for EMC issues: The PROFIBUS cable must not be run in the same tray as a 400 V power cable. If the cable must cross a power cable, do so at 90° and keep a minimum of 200 mm separation.
• Update the firmware: AUMA issues firmware updates for the PROFIBUS module that fix communication bugs. Check the AUMA support website for the latest revision before commissioning a new system.
• Pre-stage the replacement actuator: Set the address and baud rate of the spare AUMATIC before installing it. The default address is 0, which is not valid for Class 1 master communication, and a wrong address is the single most common cause of a bus fault after a maintenance swap.
• Schedule terminator checks: A terminator can become open-circuit after a vibration event. Add a check of both end terminators to the annual maintenance plan.

Frequently Asked Questions