This configuration guide consolidates the hardware, firmware, network, and engineering workflow required to deploy a Siemens SIMATIC S7-400H high-availability controller (typical selection: CPU 417-5H, 6ES7417-5HT06-0AB0) in a PROFINET ring together with ET 200SP distributed I/O stations using the IM 155-6PN HF interface module. The content targets process automation plants running SIMATIC PCS 7 or STEP 7 V5.5 with S7-H-CiR where the S2 system-redundancy relationship between the two H-CPUs and each S2-capable ET 200SP station must be parameterized, commissioned, and verified before plant handover.
1. System Architecture Overview
The S7-400H is a fault-tolerant PLC consisting of two redundant central processing units (H-CPU0 and H-CPU1) connected through fiber-optic synchronization links. Each CPU owns an integrated PROFINET interface (2-port managed switch), so that two PROFINET IO controllers exist physically but logically one set of I/O images is updated across both controllers. The ET 200SP station head-end IM 155-6PN HF is configured as a S2 device: it accepts two Application Relationships (ARs) - one from each H-CPU - and is part of a PROFINET ring that uses MRP (Media Redundancy Protocol) per IEC 62439-2. When the active H-CPU fails, the backup H-CPU takes over the AR within a defined switchover time without restarting the ET 200SP station.
Three redundancy domains coexist in this architecture:
- H-CPU redundancy: hot-standby CPUs synchronized by sync modules (6ES7960-1AA06-0XA0 for 10 m, 6ES7960-1AB06-0XA0 for up to 10 km), with 6ES7960-1AC00-0AA0 fiber-optic cables.
- PROFINET ring redundancy: MRP manager (typically a SCALANCE switch) closes the ring; the IMs and the integrated PN ports of the H-CPUs are MRP clients.
- System redundancy (S2): each IM 155-6PN HF maintains an AR to H-CPU0 (primary) and an AR to H-CPU1 (backup); the device internally arbitrates which AR is the active source of output data.
2. Bill of Materials and Hardware Components
The minimum hardware list for a single S7-400H rack controlling one PROFINET ring with ET 200SP stations is summarized below. All part numbers are Siemens MLFB (article) numbers valid for firmware 6.0.x of the CPU and firmware 3.3 or higher of the IM 155-6PN HF.
| Component | MLFB / Article No. | Function | Notes |
|---|---|---|---|
| CPU 417-5H (V6.0) | 6ES7417-5HT06-0AB0 | Primary/backup controller | 30 MB work memory, 2-port PROFINET switch integrated |
| CPU 412-5H / 414-5H / 416-5H | 6ES7412-5HK06-0AB0 / 414-5HM06 / 416-5HS06 | Smaller redundancy controllers | Selection based on program memory and cycle time |
| UR2-H rack | 6ES7400-2JA00-0AA0 | Mounting rack for 2 H-CPUs | 9 slots, segmented backplane |
| PS 405/407 power supply | 6ES7405-0KA02-0AA0 / 6ES7407-0KA02-0AA0 | Power to rack | 10 A or 20 A version |
| Sync module (FO) | 6ES7960-1AA06-0XA0 | Fiber-optic sync | Up to 10 m, two required |
| FO patch cable | 6ES7960-1AC00-0AA0 | Sync link cable | Use matched pair per CPU pair |
| IM 155-6PN HF | 6ES7155-6AU01-0BN0 | ET 200SP PROFINET head | FW 3.3+ for S2, FW 4.4+ for MRP interconnection |
| IM 155-6PN HF (extended) | 6ES7155-6AU30-0BN0 | Newer variant | FW 4.4 default, more diagnostics |
| BaseUnit BU-Send / BU-Recv | 6ES7193-6BP00-0BA0 / 6ES7193-6BP00-0DA0 | ET 200SP backplane | One per I/O module |
| SCALANCE XC206-2SFP | 6GK5206-2BS00-2AC2 | MRP manager / ring port | Manages ring reconfiguration |
| Industrial Ethernet cord | 6XV1840-2AH10 | PROFINET patch cable | Cat6A, SF/UTP |
3. ET 200SP IM 155-6PN HF Specifications
The IM 155-6PN HF is the High-Feature variant of the ET 200SP PROFINET interface module. Compared to the standard IM 155-6PN ST (6ES7155-6AU00-0AB0), the HF variant adds S2 system redundancy, MRP/MRPD client, prioritized startup, and extended diagnostics. Key electrical and functional parameters are listed in the table below.
| Parameter | Value |
|---|---|
| Article number (HF) | 6ES7155-6AU01-0BN0 (FW 3.3 / 4.0); 6ES7155-6AU30-0BN0 (FW 4.4) |
| Supply voltage | 24 V DC (20.4 to 28.8 V) |
| Current consumption | typ. 280 mA, max. 450 mA at 24 V |
| Power dissipation | typ. 6.7 W |
| Number of PROFINET ports | 2 (integrated switch) |
| Maximum I/O modules | 32 per station (max. 64 channels per module type) |
| Minimum update time | 250 µs (send clock 1 ms, reduction ratio 1) |
| Send clock supported | 1 ms (firmware 3.3+), 0.5 ms, 0.25 ms (FW 4.4) |
| PROFINET conformance class | C |
| Redundancy modes | MRP, MRPD, S2 system redundancy |
| Prioritized startup | Yes (with MRPD / 100 Mbps) |
| Isochronous mode | Yes (firmware 4.0+) |
| Cycle time for S2 AR | Identical to primary AR; default reduction ratio 4 at 1 ms send clock |
| Status LEDs | RDY, SF, BF, MAINT, PWR, LK1/2 (port status) |
The relationship between send clock, reduction ratio, and effective update time is given by:
T_update = T_send_clock × ReductionRatio
For a typical S7-400H deployment the engineer selects T_send_clock = 1 ms and ReductionRatio = 4, yielding T_update = 4 ms. The PROFINET watchdog must be set to T_watchdog = T_update × WatchdogFactor with a default WatchdogFactor = 3 (range 1 to 255 in the engineering tool). The factor of 3 is the Siemens-recommended minimum to tolerate transient jitter without triggering spurious station failures.
4. PROFINET Ring Topology with MRP Configuration
MRP (Media Redundancy Protocol, IEC 62439-2) is the layer-2 ring protocol used in SIMATIC PROFINET networks. A SCALANCE XC206-2SFP is normally assigned as the MRP manager; the two integrated PN ports of each H-CPU, all ET 200SP IMs, and any other PROFINET devices in the ring are configured as MRP clients. The ring closes through the second port of the last device back to the second port of the manager.
Ring recovery time is bounded by:
T_recovery_MRP ≤ 200 ms (default MRP)
T_recovery_MRPD ≤ 10 ms (MRP with diagnostic interrupt, requires MRPD-capable manager and FW 4.0+ on IM)
Use MRPD whenever the application tolerates fast reconfiguration but requires deterministic recovery, for example on S7-400H with safety or fast process interlocks. MRPD is supported on IM 155-6PN HF from firmware 4.0 and is mandatory if prioritized startup is enabled.
The physical cabling order is determined by the plant layout, not the engineering order. Recommended topology for an S7-400H:
- SCALANCE XC206-2SFP port 1 → H-CPU0 PROFINET port 1
- H-CPU0 PROFINET port 2 → ET 200SP station 1 IM port 1
- ET 200SP station 1 IM port 2 → ET 200SP station 2 IM port 1
- Continue daisy-chain through the remaining stations
- Last station IM port 2 → SCALANCE XC206-2SFP port 2 (closes the ring)
Document the ring ports in HW Config / TIA Portal topology view; MRP role (Manager / Client) is an attribute of the PROFINET device, not of the cable.
5. S2 System Redundancy Concept
An S2 device in the PROFINET context is a single field device that exposes two Application Relationships (ARs) simultaneously: one to the primary IO controller and one to the backup IO controller. In an S7-400H installation, the two IO controllers are H-CPU0 and H-CPU1. Both controllers receive identical input (input image is mirrored) and either may write outputs, but only one AR is in the role of primary at a given moment. The other AR is in backup state and the IM discards output writes from it.
Switchover from primary to backup is initiated by the S2 device when it detects loss of the primary AR or by a controlled handover triggered by the H-system. Typical switchover time is < 100 ms. During switchover the configured output behavior applies:
| Output behavior on AR loss | Effect on S2 device | Use case |
|---|---|---|
| Substitute value (0) | Outputs are forced to configured substitute | Fail-safe, deterministic de-energization |
| Freeze last value | Outputs hold the last received value | Continuous process (level, flow) |
| Continue (no substitute) | Outputs remain undefined until next AR | Not recommended for H-systems |
The S2 role is assigned to the IM 155-6PN HF in the engineering tool under Properties > PROFINET interface > Redundancy mode > S2. The matching redundancy role of the IO controller is set in the CPU properties as System redundancy S2; the H-CPU pair then negotiates internally which one is the primary for the S2 AR at any given moment.
6. Software Configuration Workflow (STEP 7 / PCS 7 / TIA Portal)
The primary engineering toolchain is STEP 7 V5.5 + SPx together with the S7-H-CiR add-on package (for non-PCS 7 installations) or SIMATIC PCS 7 V9.0 / V9.1. TIA Portal V16 and later supports configuration of S7-400H with PROFINET ring topologies; verify the project target with the latest TIA Portal release notes for H-CPU support.
Workflow summary:
- Create a new S7-H station with both H-CPU slots. Insert UR2-H, PS, and the two CPUs.
- Open HW Config and assign the PROFINET interface of each CPU a unique IP and a shared PROFINET device name (different S2 role per CPU). Both CPUs must be on the same IP subnet, e.g., 192.168.0.11 and 192.168.0.12 with mask 255.255.255.0.
- Insert the SCALANCE XC206-2SFP from the catalog. Assign the ring manager role and connect port 1 / port 2 to the closing ring nodes.
- Insert each IM 155-6PN HF from the catalog (or import its GSDML if the latest FW is not in the HW catalog). Configure it as an MRP client and set Redundancy mode = S2.
- Assign the IM 155-6PN HF to both H-CPUs by adding it as a PROFINET IO device under each CPU; STEP 7 will issue a warning if S2 is selected but the CPU is not part of an H-station - acknowledge only after confirming both CPU slots are configured.
- Compile and download the project. The S7-400H performs an H-linkup via the FO sync modules; only after a successful link-up are the S2 ARs established with each IM.
- Run the PC station (e.g., PCS 7 OS) against the live S7-400H to verify AR status in the diagnostic faceplates.
7. GSDML Installation and Device Description
The GSDML (Generic Station Description Markup Language) file for the IM 155-6PN HF is supplied by Siemens and updated whenever the firmware changes. The current naming convention is:
GSDML-Vx.y-Siemens-ET200SP-IM155_6PNHF-YYYYMMDD.xml
Install the GSDML in STEP 7 via Options > Install GSD File or in TIA Portal via Options > Manage general station description (GSD) files. The matching device icons become available in the device catalog under PROFINET IO > I/O > ET 200SP. After installation, restart the engineering tool so that the slot-level parameters of the new GSDML are picked up by the offline configuration.
To verify the installed GSDML matches the firmware on the physical device, compare the device's Article No. and Firmware version with the GSDML header. Mismatches can cause the engineering tool to offer slot configurations that the device will reject with a Module configuration error (PROFINET error code 0x0001 / 0x0002 in the diagnostic buffer).
8. Commissioning Sequence and Verification
Use the following sequence at first power-up of the system. Document every LED and diagnostic buffer observation on the commissioning sheet so that the as-built record matches the engineering.
- Power on the UR2-H rack. Both H-CPUs must show RDY LED green flashing during startup, then solid green after the H-linkup via sync modules.
- Verify the FO sync link with the diagnostic buffer entry "H-Sync up successful" (event ID 0x73A4 for CPU 417-5H V6.0).
- Power on the SCALANCE MRP manager. Confirm its MRP status LED is green (manager active) and the ring is closed (no partial-ring diagnostic).
- Power on each ET 200SP station. RDY LED must transition from green flashing to solid green within 5 to 15 s, depending on station size.
- Read the CPU's PROFINET diagnostics: CPU > Diagnostics > PROFINET IO diagnostics. Each IM 155-6PN HF must appear in the list with state "OK" and two ARs visible (one to each H-CPU).
- From the engineering PG, force a write/read check on at least one input and one output of every station.
- Power off H-CPU0 (simulate primary failure). Observe the redundant handover: RDY LED on H-CPU1 remains green, IM 155-6PN HF stations report "AR primary role change" in the diagnostic buffer. Total process downtime should be < 100 ms.
- Restore H-CPU0. H-system returns to redundant mode within 60 s; the active role is shared according to the configured tiebreaker.
- Cut a single ring cable. MRP recovery time observed on the SCALANCE status page. All stations must continue to communicate with both H-CPUs.
9. Diagnostics, LED Codes, and Diagnostic Buffer
Each IM 155-6PN HF reports its state on the front-panel LEDs. The matrix below is the Siemens-recommended interpretation. For full LED color/state combinations refer to the ET 200SP System Manual.
| RDY | SF | BF | MAINT | Meaning | Action |
|---|---|---|---|---|---|
| Green solid | Off | Off | Off | Station OK, S2 ARs active | None |
| Green flashing | Off | Off | Off | Startup phase, no AR yet | Wait for engineering assignment |
| Green solid | Red solid | Off | Off | Module diagnostic present (slot fault) | Read station diagnostic buffer |
| Green solid | Off | Red flashing | Off | No PROFINET connection / configuration mismatch | Check name assignment and IP |
| Green solid | Off | Red solid | Off | PROFINET bus fault (link down on both ports) | Check cabling and switch |
| Green solid | Off | Off | Yellow solid | Maintenance demanded (e.g., FW update required) | Open maintenance alarm in WinCC/PCS 7 |
| Off | Red flashing | Red flashing | Yellow flashing | Firmware update in progress | Do not power off |
Common diagnostic buffer entries on the S7-400H CPU related to the ET 200SP ring:
| Event ID | Text | Cause | Remedy |
|---|---|---|---|
| 0x0194 | PROFINET IO: Station failure | AR lost / device unreachable | Check MRP state and S2 role |
| 0x0195 | PROFINET IO: Station return | AR re-established | Informational |
| 0x011E | AR establishment error | S2 mismatch or name conflict | Re-assign PROFINET device name |
| 0x0381 | H-Sync down | Sync module FO link lost | Replace sync cable or module |
| 0x03A1 | Redundancy loss on PROFINET IO | S2 partner AR down | Verify second H-CPU and S2 config |
10. Troubleshooting Matrix
The matrix below pairs the most frequent fault symptoms observed on S7-400H with PROFINET ring ET 200SP stations to the most probable root cause and the corrective action. Use it as a field triage table during commissioning or after a process upset.
| Symptom | Most probable cause | Action |
|---|---|---|
| IM reports BF solid, no AR to either CPU | PROFINET name not assigned | Assign the configured name from the topology editor or via PRONETA |
| IM reports BF flashing, AR to one CPU only | S2 role enabled on device but not on the second CPU | Enable "System redundancy S2" on both H-CPUs |
| Ring cut, but station reports "Station failure" for 2 to 3 s | MRP not active, manager missing | Configure SCALANCE as MRP manager, IM as MRP client |
| CPU 0 fails, no handover | Sync module defective or FO link loose | Check LED on sync module (LINK) and reseat cable |
| Output of IM does not update after AR switchover | Substitute value behavior active and no backup values | Change output behavior to "Freeze last value" for the affected channel |
| High jitter on PROFINET, late diagnostics | Send clock too low for line topology | Increase send clock to 1 ms; set reduction ratio to 4 or 8 |
| PROFINET device name conflict | Two devices assigned same name | Reset device to factory, reassign unique name |
| Spurious diagnostic alarms during cold start | Prioritized startup enabled on slow stations | Disable prioritized startup on non-essential stations or upgrade to FW 4.4 |
11. Network Security and Hardening
An S7-400H with PROFINET ring in a PCS 7 plant must be hardened per the IEC 62443 zone-and-conduit model. The PROFINET ring is a critical conduit and shall not be exposed directly to the office network. Recommended measures:
- Place a SCALANCE S615 or SCALANCE SC-600 security module between the PROFINET ring and any upstream network (e.g., PCS 7 OS / Engineering station).
- Disable unused PROFINET services on the IM 155-6PN HF, especially DCP read and SNMP, when not needed for diagnostics.
- Use PROFINET device-name assignment only via the authorized engineering PG; disable unconfigured PROFINET devices from accepting new names by setting a name-assignment ACL on the SCALANCE.
- Sign and verify the engineering project with the S7-H-CiR project signing function to detect unauthorized configuration changes.
- Apply the latest Siemens security patches to PCS 7 / STEP 7; both are listed in the Siemens ProductCERT advisories.
For firmware updates use the SIMATIC Automation Tool or the TIA Portal "Update firmware" wizard. Verify the new firmware on the IM 155-6PN HF supports S2 with the S7-400H CPU firmware in use; consult the Siemens compatibility tool prior to deployment.
12. Frequently Asked Questions
Which firmware version of IM 155-6PN HF is the minimum for S2 system redundancy with an S7-400H?
Firmware V3.3 (article 6ES7155-6AU01-0BN0) is the minimum that supports S2. For MRP Interconnection, prioritized startup, and 0.25 ms send clocks, use V4.4 (6ES7155-6AU30-0BN0). Always cross-check against the Siemens compatibility tool for the specific CPU firmware.
Can the same ET 200SP station be assigned to both H-CPUs automatically by STEP 7?
Yes. In HW Config you insert the IM 155-6PN HF as a PROFINET IO device once and assign it to both H-CPU PROFINET interfaces. STEP 7 then generates the S2 ARs; the "System redundancy S2" flag on each CPU's PROFINET interface must be enabled.
What is the typical switchover time when H-CPU0 fails?
The S2 handover from primary to backup AR on the IM 155-6PN HF completes in less than 100 ms under nominal conditions. The overall H-system switchover of the CPU pair (sync-link down to backup becoming primary) typically finishes within 100 to 300 ms, depending on program length and current cycle time.
Is MRP mandatory on an S7-400H PROFINET ring with ET 200SP?
Yes. Without MRP (or MRPD) a single cable break disconnects all stations downstream of the break. MRPD further reduces recovery time to under 10 ms and is recommended for safety and fast process interlocks.
Where can I download the official GSDML for the IM 155-6PN HF?
Use the Siemens Industry Online Support (support.industry.siemens.com) entry search "6ES7155-6AU01-0BN0" or the ET 200SP System Manual PDF on the SIOS portal. The full ET 200SP system manual is also distributed as a PDF mirror through Mouser Electronics ET 200SP System Manual for reference during offline engineering.