Resolving Siemens MP370 Profibus DP Error 140015 on CPU314C-2DP

Overview

When a SIMATIC MP370 multi-panel is configured for Profibus DP communication to a SIMATIC S7-300 CPU314C-2DP, the runtime on the panel may report a connection-failed message followed by error code 140001 "Connection disconnected" and 140015 "Incorrect baud rate or interrupt number set" approximately 15-20 seconds after start-up. The same error pattern appears in two common misconfigurations: the user has selected the wrong transfer channel in ProTool/Pro, or the bus has been wired with the wrong port of the CPU. The fault is traceable to one of four areas - transfer/protocol mode on the MP370, Profibus address or baud rate in STEP 7 and ProTool/Pro, the physical bus (cable, connector, termination), or the operating-mode setting "Panel is only master on the bus" in the panel's transfer configuration.

This reference walks through the failure mode, the two error codes involved, the exact check points in ProTool/Pro CS V6.0 SP3 and STEP 7, and a verification procedure that confirms the link end-to-end. The article also includes a diagnostic matrix that maps error to root cause to action, plus an end-of-life migration note for projects that move to WinCC flexible.

Affected Hardware and Software

The MP370 ports referenced in this article are:

• X1 (IF1B / MPI-DP) - 9-pin Sub-D, the combined MPI/Profibus DP port used for the PLC link.
• X2 (IF2) - Ethernet RJ45, present only on units ordered with the Ethernet option (6GK1 164-0AA00 or 6GK7 164-0AA00-0AB0).

The CPU 314C-2DP's two ports are:

• X1 - MPI/DP combined (default MPI, can be configured as DP via STEP 7 hardware configuration).
• X2 - Profibus DP master/slave. This is the port that must be used for the MP370 link when the CPU is the master.

Error Code Reference

ProTool/Pro Runtime and the WinCC flexible Runtime on the MP370 share a common error-numbering block. The two codes that appear in the start-up sequence are members of the connection-status group 140000-140099.

The "interrupt number" referenced by error 140015 is the diagnostic-interrupt OB82/OB40 number that ProTool/Pro writes into the transfer parameter set. When the panel is configured as a DP master that owns the bus ("Panel is only master on the bus" = ON), it must be assigned an interrupt slot. If the slot conflicts with the CPU 314C-2DP's diagnostic frame, the panel's bus parameter set is rejected and the connection never opens. If the panel is configured as a master that shares the bus with the CPU, the slot must still match the slot referenced in the partner's Profibus configuration in STEP 7. Mismatch is a frequent cause of 140015 even when the baud rate is correct.

The 15-20 second window between the "Change operating mode to online" message and the error is the bus-parameter negotiation timeout. The MP370 listens on the configured baud rate for the master's parameter frame. If the frame is not seen within that window, the panel raises 140015 and falls back to the offline screen.

Root Cause Analysis

Error 140001 + 140015 at start-up is a layered fault. The six root causes observed in field service, in roughly decreasing frequency:

1. Wrong port selected in the MP370 transfer settings. The MP370 has one combined MPI/DP port (X1). The active protocol is selected in ProTool/Pro under Transfer Settings > Advanced > Properties. If the project was downloaded for MPI, the panel will drive X1 as MPI. The CPU 314C-2DP's X2 port cannot accept an MPI handshake, so the bus is silent from the panel's point of view and 140011 or 140015 is raised.
2. Profibus address collision. Both devices have been assigned address 2 (factory default for the CPU), or the CPU's DP port has been assigned the panel's default address of 1 in a way that creates a duplicate. The bus master rejects one of the slaves and 140015 is raised.
3. Baud rate mismatch between STEP 7 and ProTool/Pro. ProTool/Pro defaults to 1.5 Mbps, but the STEP 7 hardware configuration of the CPU 314C-2DP's DP interface may be set to 187.5 kbps, 45.45 kbps, or "Auto-detect" that resolves to a different value. The panel sees a quiet bus within 140015's negotiation window.
4. Bus termination or cable fault. Termination resistors ON at both end nodes, or OFF at the end nodes. Cable length outside the 12 Mbps to 9.6 kbps specification. A shield broken at a connector. The result is reflection-induced CRC errors that the panel counts as "no bus".
5. "Panel is only master on the bus" set incorrectly. If this checkbox is ON, the panel is configured as the sole bus master. The CPU 314C-2DP cannot simultaneously be a master on the same bus. If the user has wired the link expecting the CPU to be the master, the bus parameter frame from the CPU is not accepted by the panel and 140015 is raised. The inverse case is also true: if the checkbox is OFF but the CPU has not been configured as a master (or the wrong CPU is the master), the panel will not enter the bus and 140015 is raised.
6. Incompatible ProTool/Pro Runtime image or wrong device type in the project. If the project was created for an MP370-15 Touch but flashed onto an MP370-12 Key, the transfer image can be loaded but the bus driver will not initialise. The panel raises 140015 within 20 seconds. The version stamped on the panel boot screen and the device type in ProTool/Pro must match exactly.

Diagnostic Procedure

The fastest path to a confirmed root cause is a three-stage pass: PG/PC interface, project parameters, physical bus. Run the stages in order and stop at the first failure.

Stage 1 - Confirm the panel is reachable from the engineering station

Open ProTool/Pro CS, select Options > Set PG/PC Interface and verify that the S7ONLINE access point is bound to a Profibus or PC adapter that is known good. If the panel can be reached via "Accessible nodes" (or Online > Accessible Nodes in the case of STEP 7 with the SIMATIC Manager open), the panel's bus interface is alive and the issue is at the parameter level. If the panel does not appear, the fault is hardware or wiring and you can move to Stage 3.

The Siemens entry-level FAQ 19378851 walks through the "Accessible nodes" procedure for both ProTool/Pro and STEP 7 and covers most of the bus-level problems that surface in this scenario.

Stage 2 - Project parameter review

Open the project in ProTool/Pro CS V6.0 SP3. Navigate to Panel > Transfer > Transfer Settings. Two sub-tabs are critical:

• Channel - the active bus (MPI, DP, Ethernet) and the bus address.
• Advanced > Properties - the operating-mode switch "Panel is only master on the bus" and the interrupt number.

Record the following into a worksheet before changing anything:

Open the STEP 7 project, expand the CPU 314C-2DP in the hardware configuration, and double-click the DP interface. In the Properties > Profibus dialog, record the master's address, baud rate, HSA, and bus profile. Then open DP slave properties for the MP370 (the slave must be added from the catalog: SIMATIC HMI > MP370). Verify the same baud rate and bus profile.

Any mismatch in step 1 (DP vs MPI) or step 2 (address, baud rate, master flag) is the fault. Fix the project, recompile, transfer, restart.

Stage 3 - Physical bus inspection

• Confirm the cable is purple Profibus cable, 6XV1 830-0AH10 or compatible. Standard RS-485 cable is not a substitute.
• Confirm both end-of-segment connectors have termination ON (switch set to "ON" at the connector body) and all intermediate connectors have termination OFF.
• Measure the resistance between pin 3 and pin 8 of any connector. It should read approximately 220 ohm at each end of the segment and approximately 110 ohm measured at any intermediate node.
• Inspect the shield clamp. The shield must be clamped to the connector body on both ends of the cable. A floating shield is a common source of intermittent faults.
• Confirm the cable is in the support duct and not bundled with power cables for more than a few centimetres.

Configuration - ProTool/Pro CS V6.0 SP3

Transfer settings for DP

1. Start ProTool/Pro CS V6.0 SP3. Open the project.
2. From the Panel menu, choose Transfer > Transfer Settings.
3. In the Channel sub-tab, set:
   • Transfer channel: DP
   • Address of panel: 1
   • Baud rate: 1.5 Mbps (or match STEP 7)
4. Open Advanced > Properties and set:
   • Panel is only master on the bus: cleared (unchecked), unless no other master exists on the bus.
   • Interrupt number: any value between 0 and 31 not already in use. ProTool/Pro will warn if the value conflicts with the partner's slot. Common safe value: 16.
5. Click OK. Save the project. Recompile (Ctrl+F9 or File > Compile).
6. Transfer the project to the panel via Project > Transfer > Transfer to Panel or by using the PLC's online download.

Transfer settings for MPI fallback

If the project is to be run on MPI for diagnosis, change the Transfer channel to MPI, set the baud rate to 187.5 kbps (default for MPI on the CPU 314C-2DP X1 port), and reconnect the cable to the CPU's X1 port. Note that the MP370's X1 port is the same physical connector in both cases - the protocol is set by software, not by a pin strapping.

Configuration - STEP 7

CPU 314C-2DP hardware configuration

1. Open the STEP 7 project that owns the CPU 314C-2DP. In the SIMATIC Manager, open the S7 station and double-click Hardware.
2. The CPU 314C-2DP is in the catalog under SIMATIC 300 > CPU 300 > CPU 314C-2DP. The exact order number to drag in depends on the FW version of the physical CPU; 6ES7 314-6CF02-0AB0 and 6ES7 314-6CG03-0AB0 are the most common in the field.
3. Drag the CPU into the rack. STEP 7 creates a subrack with the integrated DI16/DO16/AI5/AO2 in slots 0-3 automatically.
4. Open the DP interface (X2) object. In the Properties > Profibus dialog:
   • Address: 2 (default for the CPU)
   • Subnet: New Profibus subnet, "PROFIBUS(1)"
   • Subnet properties > Network settings:
     • Baud rate: 1.5 Mbps
     • Highest station address: 126
     • Bus profile: DP (Universal)
5. From the catalog, navigate to SIMATIC HMI > MP370. Two slaves appear: MP370 Touch and MP370 Key. Drag the variant that matches the physical panel into the DP subnet. STEP 7 will assign the next free address; change it if required.
6. Open the slave's Properties and confirm the baud rate matches the master and that the Slot dialog lists the configured interrupts.
7. Compile and download the hardware configuration to the CPU (PLC > Download to Target System).

Parameter alignment with ProTool/Pro

If the user wants the MP370 to be the sole master, the Panel is only master on the bus must be ON, the CPU's X2 port must not be configured as a DP master (or, in the rare case of a passive CPU port, the bus must terminate at the panel). In the case described, the user has confirmed the checkbox is ON. This is incompatible with a CPU 314C-2DP configured as the DP master on the same bus. The fix is to uncheck the box, save, recompile, and re-transfer.

Wiring and Bus Topology

Connector pinout (MP370 X1 / CPU 314C-2DP X2)

Reference topology for CPU 314C-2DP and MP370

+--- CPU 314C-2DP X2 ---+              +----- MP370 X1 -----+
| 9-pin Sub-D           |              | 9-pin Sub-D        |
| Term = ON (if end)    |==============| Term = ON (if end) |
| Address = 2           |  Profibus    | Address = 1        |
| Baud = 1.5 Mbps       |  cable       | Baud = 1.5 Mbps    |
+-----------------------+  6XV1 830    +---------------------+
                        Ah10
- One terminator ON at the left connector, one terminator ON at the right connector.
- No terminator ON in the middle of the cable run.
- Maximum segment length at 1.5 Mbps: 200 m.
- Maximum segment length at 12 Mbps: 100 m.

If the panel is not the last device on the segment, the termination at the panel must be OFF. The cable must continue to the next node. The total segment length is counted from the first terminator to the last.

Resolution Steps

The following procedure resolves the reported fault in over 90% of field service calls. Run in order; do not skip the verification step at the end.

Step 1 - Confirm the panel boots and that the firmware image matches

Cycle power on the MP370. Watch the splash screen. Confirm the device type printed on the splash (e.g. "MP370 12" Touch"). Compare with the project device type in ProTool/Pro. If they differ, the wrong Runtime image was flashed; the panel will not initialise the bus driver and 140015 is reported within 20 s.

Step 2 - Open the panel's control panel and check the bus state

On the MP370, open the Control Panel (the Windows CE / CE-Panel control panel, not the runtime). Open Transfer (or MPI/DP Interface depending on firmware). The dialog displays the currently active protocol, the bus address, and the baud rate. The values are read from the panel's persistent settings, not from the project. If the values do not match the project, the most recent transfer did not write them; re-transfer the project.

Step 3 - Verify the protocol selection matches the wiring

The MP370's X1 port is software-selected. If the project is for MPI but the cable is on the CPU's X2 (DP) port, the bus is silent from the panel. The same is true in reverse. Match the protocol to the connector:

If you want to test the link on MPI as a quick sanity check, change the project's Transfer channel to MPI, recompile, transfer, and reconnect the cable to CPU X1. The error 140015 should disappear. If it does, the wiring is correct and the issue is at the DP level. If 140015 still appears on MPI, the fault is hardware (connector, cable, panel X1 port, CPU X1 port).

Step 4 - Audit Profibus address assignment

Open the panel's control panel and the STEP 7 hardware configuration. Both must agree on the panel's DP address. Default values that frequently collide:

If the CPU is address 1 (rare, but happens after a factory reset) and the panel is also 1, the bus rejects one. Re-address the panel to 5 or 8 in ProTool/Pro, recompile, re-transfer, and re-download the STEP 7 hardware configuration to the CPU.

Step 5 - Audit baud rate alignment

In ProTool/Pro: Panel > Transfer > Transfer Settings > Channel > Baud rate. In STEP 7: Hardware > DP Interface > Properties > Profibus > Subnet properties > Network settings > Transmission rate. Both must show the same value.

If the user has a Profibus cable in the same duct as an AS-i cable, or a Profibus network that includes a gateway to a 12 Mbps backbone, the subnet can be in 12 Mbps mode while the panel is at 1.5 Mbps. Set both to the same value. Save, recompile, re-transfer.

Step 6 - Resolve the "Panel is only master on the bus" flag

If the CPU 314C-2DP is to be the master (the normal case), the flag in ProTool/Pro must be UNCHECKED. The user has confirmed it is currently checked. Uncheck the box, save the project, recompile, transfer, and restart the panel.

If the panel is to be the sole master (rare, only used in panels that own the bus and do not have a CPU as master), keep the flag checked. In this case the CPU's DP port must be configured as a slave, not a master. The CPU 314C-2DP supports slave mode on X2; the setting is in the same Properties dialog as the master address.

Step 7 - Re-verify the bus physically

Power down the panel and the CPU. Inspect the cable. Confirm terminations. Power up. Watch the panel's splash screen and the bus status LED on the CPU's X2 port (where present) - the LED will flicker in 5 s intervals if the bus is alive.

Verification

The link is considered healthy when all of the following are true. Verify each in order.

1. The panel boots into the project, not the control panel. The runtime is running.
2. The "Change operating mode to online" message does not appear within 30 s of boot.
3. No error 140001 or 140015 is logged in the runtime's alarm view.
4. STEP 7 Online > Accessible Nodes lists the MP370 as an active DP node. The address matches the project.
5. A tag from the CPU is visible on a screen of the panel. Example: create a tag in ProTool/Pro of type "Word", connected to DB1.DBW0, and place it on a screen. Toggle the value from STEP 7 (VAT) and confirm the panel updates within 2 s.
6. With a Profibus analyzer connected to the bus (PROFIBUS Tester BC-700-PB or similar from Softing), the bus is in OPERATE state, not CLEAR. The token rotates between the master (CPU) and the slave (panel). Each device is sending at the configured baud rate.

If the link passes 1-5, the application is online. If only 1-4 pass and 5 fails, the bus is up but the tag is not configured. Re-check the ProTool/Pro tag database, the connection editor, and the address-area mapping (DB, MW, I, Q, T, C, or absolute PI/PQ for S7-400).

Advanced Diagnostics

Profibus diagnostics via the panel

The MP370 control panel exposes a Bus Diagnostics or MPI/DP Diagnostics applet on the latest images. The applet shows the bus activity for the last 60 s. If the counter is 0, the bus is silent. If the counter is high but CRC errors are non-zero, the bus is alive but electrical quality is poor. CRC errors > 5% require cable and termination inspection.

Profibus diagnostics via STEP 7

Open the STEP 7 project online. Open the CPU 314C-2DP's DP Interface > Diagnostic. The dialog shows:

Profibus diagnostics via a tester

The Softing PROFIBUS Tester BC-700-PB, the Indu-Sol PROFIBUS-INspektor, or the Siemens PROFIBUS Diagnostics Repeater (6ES7 972-0AB01-0XA0) can be placed in the bus to capture frames. Look for:

• The Master's parameter frame (FSD/FMA).
• The Slave's RDY response (low to high within 100 ms of master power-up).
• The diagnostic request from the master.
• The slave's diagnostic response.

A healthy bus at 1.5 Mbps will show a frame rate of approximately 1000 to 1500 frames per second in a minimal configuration (master + one slave).

Error code 140015 and the diagnostic interrupt slot

In ProTool/Pro, the Interrupt number is the diagnostic interrupt number that the panel will use if it is configured as a DP master. If the number is set to a value that the CPU 314C-2DP is using for a slot-level diagnostic interrupt, the bus parameter negotiation fails. The error is logged on the CPU's diagnostic buffer as "DP slave: parameter assignment error". To resolve, set the interrupt number in ProTool/Pro to a value that is not used by any slave in the STEP 7 hardware configuration. 16 is a safe default.

Operating Mode "Panel is only master on the bus" - Decision Matrix

The reported configuration - flag is ON, CPU is the master - is the most common field error. The fix is to uncheck the flag and re-transfer. If the flag is left ON, the bus is operated in single-master mode, and the CPU's parameter frame is not accepted. The panel raises 140015 within 15-20 s.

Migration Considerations

The MP370 is a legacy product. The hardware is in the "classic" phase of SIMATIC HMI, and ProTool/Pro is no longer developed. The forward migration is to WinCC flexible 2004 SP1+ (or WinCC V7 for SCADA projects). A MP370 project must be migrated with Project > Migrate in WinCC flexible, not simply re-pointed. The migration tool will warn of unsupported features. After migration, repeat the same diagnostics:

• Verify the Connection in the WinCC flexible project is configured for SIMATIC S7 300/400 > PROFIBUS.
• Verify the bus address in the connection matches the panel's transfer settings.
• Verify the baud rate in the connection matches the STEP 7 hardware configuration.

WinCC flexible uses the same error-code space for connection faults. Error 140001 and 140015 are the same code and the same meaning.