Troubleshooting FM 458-1DP Profibus DP Slot Not Highlighted

Problem Overview

The FM 458-1DP (Siemens order number 6DD1607-0AA2, firmware V2.1.1) is an application module designed for high-speed closed-loop control, motion control, and PROFIBUS-DP communication within a SIMATIC S7-400 rack. When installed in the same ET 200 / S7-400 rack as a CPU 416-3XR05-0AB0, the FM 458-1DP is configured to communicate with an ABB drive (such as an ACS800 or ACS880 family unit) over the integrated PROFIBUS-DP interface.

The reported fault condition: after compiling, downloading, and going online with STEP 7 / SIMATIC Manager, the PROFIBUS-DP master/slave slot on the FM 458-1DP is not highlighted (no green online indicator) and STEP 7 reports no diagnostic error for the FM 458-1DP. The same ABB drive communicates correctly when addressed through the CPU 416-3XR05-0AB0 in the same rack, ruling out cabling, addressing, ABB parameter settings, and PPO type mismatch as root causes.

Affected Hardware and Firmware

The FM 458-1DP operates as an intelligent DP slave or DP master depending on the user program and the configuration of the @PRODP function block. Without correct program-side configuration, the DP interface does not initialize and remains silent — which is exactly the symptom observed (no highlight, no error).

Root Cause Analysis

The PROFIBUS-DP interface on the FM 458-1DP is program-controlled. Unlike the CPU 416 integrated DP interfaces, the FM 458-1DP only enters the operational PROFIBUS state when the application program contains the proper initialization and cyclic data blocks. The Siemens manual explicitly states that for PROFIBUS communication on the FM 458-1DP the COM database is initialized by the user program, not by HW Config alone.

When the COM database is missing or inactive at the time of download, the DP slot on the FM 458-1DP is shown as configured but stays grayed out / inactive in online view, and the module does not participate in PROFIBUS token passing. The absence of a diagnostic error is normal in this state because the module never transitioned to operational mode.

Common Root Causes

1. Missing @PRODP block in the FM 458 user program. Without this block, the FM 458-1DP does not act as a PROFIBUS node.
2. Missing CTV / CRV (or CTV_P / CRV_P) data blocks. These configure cyclic send/receive telegrams to the DP slave. The number of PZD words must match the PPO type configured on the ABB drive.
3. PROFIBUS address mismatch or duplicate on the FM 458-1DP master port vs. CPU 416 DP port.
4. HW Config slot assignment for the FM 458-1DP DP port is left empty or assigned to the wrong logical address range.
5. Firmware / catalog mismatch. Firmware V2.1.1 may not be selectable in the standard Hardware Catalog, requiring a manual entry or a GSD import for the FM 458-1DP under STEP 7 V5.5 or earlier.
6. KF LED status: if the KF (communication fault) LED is ON or flashing, the FM 458-1DP has detected a startup or configuration error.

Diagnostic Indicators

Status LEDs on FM 458-1DP

If the KF LED is ON after download, the FM 458-1DP firmware has not received a valid COM database. This is the single most common reason the DP slot stays inactive.

STEP 7 / SIMATIC Manager Online Diagnostics

• Open HW Config, right-click the FM 458-1DP, and select Module Information → Diagnostics Buffer.
• Read ELC (error location) and ECO (error code) entries from the FM 458 diagnostic buffer. ELC/ECO are reported through the FM 458 operating system and pinpoint configuration vs. runtime errors.
• If the diagnostic buffer is empty and the module status is OK, the issue is program-side: the @PRODP and CTV/CRV blocks have not been downloaded or are not being called in OB1 / the cyclic task.

Solution: Configure the FM 458-1DP PROFIBUS Correctly

The FM 458-1DP PROFIBUS interface requires three coordinated configuration steps in HW Config and three corresponding program-side blocks. All three must be consistent.

Step 1 — HW Config: Assign the DP Master Port

1. Open the S7 project in SIMATIC Manager.
2. Open HW Config and double-click the FM 458-1DP in the rack.
3. Switch to the DP tab and enable the DP master interface on the FM 458-1DP.
4. Assign a unique PROFIBUS address to the FM 458-1DP master port. This address must differ from the CPU 416-3XR05-0AB0 DP master address and from every slave on the segment.
5. Set the transmission rate consistent with the ABB drive (typically 1.5 Mbps or 12 Mbps for ABB ACS drives).
6. Attach the ABB drive as a DP slave on this PROFIBUS subnet. Select the matching ABB GSD file and PPO type.
7. Note the I-addresses and Q-addresses STEP 7 assigns to the ABB drive — these will be referenced in the CTV/CRV blocks.
8. Save, compile, and download the HW Config to the rack.

Step 2 — Program the @PRODP Block

The @PRODP block initializes the FM 458-1DP PROFIBUS interface and starts the DP master. Without this block call, the FM 458-1DP will never enter the PROFIBUS operational state.

• Insert the @PRODP block (FB / SFB from the FM 458 standard library) into the cyclic task (OB1 or the FM 458 cyclic interrupt OB).
• Wire the configuration parameters: DP mode (master / slave), baud rate, bus parameters, and the symbolic names of the CTV/CRV blocks.
• Ensure the @PRODP instance DB is downloaded with the rest of the program.

Step 3 — Configure CTV / CRV (or CTV_P / CRV_P) Blocks

The CTV (cyclic transmit) and CRV (cyclic receive) blocks define the actual process data exchanged with the ABB drive. The variants CTV_P and CRV_P are pointer-based versions used when addresses are computed dynamically.

The number of PZD must be identical on both the FM 458-1DP side (CTV/CRV block parameters) and the ABB drive side (parameters in drive parameter group 51 or 53, depending on drive family). Mismatched PZD counts cause the PROFIBUS slave to enter a configuration error state without necessarily reporting it on the FM 458 side.

Step 4 — Compile and Download

1. Compile the S7 program (Blocks container).
2. Download the entire station (HW Config + Blocks) to the S7-400 rack.
3. Switch the FM 458-1DP from STOP to RUN.
4. Observe the KF LED — it must go OFF once the COM database is active.
5. Refresh the online view in HW Config. The FM 458-1DP DP slot should now be highlighted (green) and the ABB drive should appear online.

Working Code: CTV_P and CRV_P Block Calls

The following STL snippets show a typical configuration for a 6-word PPO with an ABB ACS880 drive. Adapt the address constants to match HW Config.

// Cyclic transmit block: data TO ABB drive
CALL  CTV_P
       NR     := 1                  // CTV instance number
       QADDR  := W#16#100           // Base output address from HW Config
       PZD    := 6                  // 6 PZD words to drive
       STATE  := MW 200            // CTV state word

// Cyclic receive block: data FROM ABB drive
CALL  CRV_P
       NR     := 1                  // CRV instance number (must match CTV)
       IADDR  := W#16#100           // Base input address from HW Config
       PZD    := 6                  // 6 PZD words from drive
       STATE  := MW 210            // CRV state word

// Initialize the PROFIBUS master on FM 458-1DP
CALL  @PRODP
       MODE   := B#16#1            // 1 = DP master
       BAUD   := B#16#6            // 12 Mbps (see manual for code table)
       BUSADDR:= B#16#2            // FM 458-1DP master address 2

The exact mode / baud / address encoding is documented in the FM 458-1DP manual chapter 4.4 (PROFIBUS). Refer to the official PDF for the complete code tables.

Verification Procedure

1. LED check: SF = OFF, BF = OFF, KF = OFF, RUN = ON (green), STOP = OFF.
2. Online slot: In HW Config online view, the FM 458-1DP DP slot is now highlighted (green).
3. Slave online: The ABB drive appears online with green check; double-clicking it shows the configured PPO type and I/Q addresses.
4. Diagnostic buffer: No new ELC/ECO entries; existing entries from previous attempts can be cleared.
5. Cyclic data: Toggle a control bit in the CTV area and confirm the ABB drive responds (e.g., status word bit 0 transitions or RUN LED on drive energizes).
6. Watch CTV/CRV STATE words: a value of 0 or a small positive number indicates healthy cyclic exchange; a non-zero error code indicates configuration mismatch.

Comparison: FM 458-1DP vs. CPU 416 Integrated DP

This contrast explains why the same ABB drive works perfectly through the CPU 416 integrated DP port — the CPU handles DP initialization transparently, whereas the FM 458-1DP requires explicit program-side setup.

Troubleshooting Matrix

Common Configuration Mistakes to Avoid

• Configuring the ABB drive as a slave on the CPU 416 DP master while also expecting it to appear under the FM 458-1DP master. Each DP master maintains an independent slave list.
• Setting the same PROFIBUS address on the FM 458-1DP master and the CPU 416-3XR05-0AB0 DP port. Use a different address for each.
• Defining PPO type 4 on the ABB drive but only 4 PZD in the CTV/CRV blocks. ABB PPO type 4 carries 6 PZD; PPO type 1 carries 4 PZD.
• Forgetting to call @PRODP from the FM 458 cyclic task (not the CPU 416 OB1). The FM 458 runs its own program; the CPU program does not initialize the FM 458 DP port.
• Downloading only the S7 Blocks container without re-downloading HW Config after changing the DP configuration.

Reference Documentation

• Siemens FM 458-1 DP Application Module Manual — primary reference for DP configuration, CTV/CRV, @PRODP, and COM database diagnostics.
• SIMATIC S7-400 FM 458-1 DP manual, chapter 4.4 — PROFIBUS configuration and diagnostic flow.
• STEP 7 / SIMATIC Manager online help for HW Config DP master setup.
• ABB ACS800 / ACS880 PROFIBus Adapter User's Manual — PPO type definitions and parameter groups 51/53.

FAQ