MM440 Replacement Drive Commissioning on S7-400H PROFIBUS Y-Link

Problem Overview

When a Siemens MicroMaster 440 (MM440) drive fails inside an S7-400H redundant PLC network that uses a Y-link on the PROFIBUS segment, the question of fast, central parameter replacement becomes critical. Operators want a spare MM440 powered up and parameterized with only a few clicks from the engineering station - not a manual walk to the cabinet with a handheld BOP, and certainly not a re-commissioning with the full STARTER download wizard for every fault.

Three workable paths exist, but only one satisfies the "few mouse clicks from a central place" requirement:

1. Store the parameter set on a BOP / AOP and write it back to the replacement - local, cheap, but not "central".
2. Use Drive ES (with STEP7 integration) to push parameters down via PROFIBUS - central, but you need a working bus connection past the Y-link.
3. Use a PROFIBUS DPV1 acyclic upload from the engineering station to a known-good master, then write back to the replacement through the same mechanism.

Topology - S7-400H, Y-Link and MM440

The S7-400H redundant controller has two PROFIBUS DP master interfaces (CP 443-1 / IM 467). On the DP1 segment both CPUs share the bus; redundant slaves (e.g. ET 200M with redundancy-capable IM 153) live here. The Y-link (e.g. 6ES7 197-1LA04 or 6ES7 197-1LA12) is inserted in DP1 and exports a lower-priority PROFIBUS segment (DP2) onto which single-channel slaves are connected.

The implication is that any Drive ES service coming from STEP7 must cross the Y-link first. Y-links pass standard DP-V0 cyclic traffic transparently, and they also pass DP-V1 acyclic services if the Y-link firmware supports it (firmware V3.x and above on 6ES7 197-1LA12).

MM440 PROFIBUS Communication Basics

The MM440 presents itself on PROFIBUS using PPO types (Parameter / Process data Objects). The two practical choices for a drive controlled from STEP7:

For central parameter download you need at least PPO 1 - the PKW channel (parameter identifier value) is what Drive ES uses to issue Read / Write requests. PPO 3 and PPO 4 cannot read or write individual parameters cyclically, which forces acyclic DPV1 access and is slower. Configure PPO 1 unless the customer explicitly wants high-speed control word switching.

Relevant MM440 parameters for PROFIBUS:

Prerequisites

Before a replacement MM440 can be commissioned centrally, confirm the following:

• STEP7 V5.5 SP4 (or TIA V13+ if the H-station has been migrated) is installed on the engineering PC, with the matching H-CPU Add-on for STEP7.
• Drive ES V5.5 SPx or STARTER V4.x with the Drive ES STEP7 plug-in installed. Drive ES adds the "Commissioning" and "Parameter download to drive" buttons directly into HW Config.
• The MM440 GSD file (SIEM80C5.GSD or SI0180C5.GSD for PPO1) is installed in STEP7 and the device is in HW Config under the Y-link DP2 segment.
• Y-link firmware supports DPV1 acyclic services (article number 6ES7 197-1LA12 with firmware V3.0 or higher). Older 1LA04 versions are DP-V0 only and block Drive ES parameter upload.
• A current parameter backup file exists. Either an offline Drive ES backup (.dnx / .par) on the engineering PC, or a saved BOP image. Drive ES will not invent the parameters - it needs a source.
• The PROFIBUS address of the replacement drive is known and unique on DP2.

Method 1 - BOP / AOP Backup and Restore (Local, Cheap)

The MM440 supports parameter upload and download through the BOP (Basic Operator Panel, 6SE6400-0BP00-0AA0) using parameters P0010 and P0011. This is the lowest-cost fallback but it is not central - the operator must go to the cabinet.

Save procedure (on the working drive):

1. Set P0010 = 0 (drive must be in ready state).
2. Set P0011 = 1 (lock the parameter set so the BOP cannot overwrite it accidentally).
3. On the BOP hold the FN key, then press P for ~3 s until "-SAvE-" appears, release both.
4. Wait for "-END-" confirmation. The BOP EEPROM now holds the parameter set.

Load procedure (on the replacement):

1. Power up the replacement MM440, leave command source disabled.
2. Set P0010 = 0, then P0011 = 2 if the locked set must be unlocked before write.
3. On the BOP hold the FN key, then press the up-arrow for ~3 s until "-LoAd-" appears, release both.
4. Wait for "-END-". The drive reboots with the saved parameter set.

Method 2 - Drive ES Central Commissioning (Recommended)

Drive ES integrates STARTER into STEP7's HW Config. Once the MM440 is in the project, right-clicking the device gives a "Commissioning" entry which opens STARTER against the live drive. From there, an offline parameter set can be pushed with Download to Drive.

Step-by-step procedure

1. Open STEP7, load the offline project for the S7-400H station that contains the failed MM440. Open HW Config and navigate to the DP2 segment below the Y-link. Verify the MM440 is present at the expected address.
2. Mark the MM440 in the DP2 rack view. Right-click -> "Open Object with STARTER / Drive ES". This launches the drive commissioning tool against the live PROFIBUS node.
3. Go online in STARTER. Confirm the connection status turns green and STARTER reads the actual topology. If the connection fails, see the troubleshooting matrix below - typical causes are wrong PPO type, missing DPV1 capability on the Y-link, or a different PROFIBUS address on the replacement.
4. Save the parameter set from the working drive (or load the last offline backup from .\Project\Drives\MM440_07.par): in STARTER click Load drive parameters to PG/PC. Save the resulting file with version stamp (e.g. MM440_add07_2024-05-12.par).
5. Hot-swap the drive. Remove the defective MM440, install the spare, terminate the bus connector, set the PROFIBUS address on the new unit (P0918) to match the address of the failed drive (default factory address is 3, almost never the right number). Use the BOP for this single value; it is a one-time local action.
6. Power the new drive and verify PROFIBUS comes up (BF LED off, RDY LED green or yellow on the CP443-1 slave diagnostics).
7. Open Drive ES against the new node. The drive object should appear with the new serial number and "Defaults loaded" state.
8. Click "Download to Drive", accept the comparison dialog, and confirm. Drive ES writes the parameter set through DPV1 acyclic services over PROFIBUS. The download typically takes 4-12 seconds for a full MM440 parameter set.
9. Save parameters to drive non-volatile by setting P0010 = 30 momentarily (factory reset) is not required; instead Drive ES performs the RAM to EEPROM copy automatically as part of "Copy RAM to ROM".
10. Verify with the next section's checklist.

Why Drive ES works on the Y-link

The Y-link accepts DPV1 acyclic read/write (Class 1 services from the DP-V1 master on DP2) provided the Y-link firmware is V3.0 or later on the 1LA12. Drive ES issues a DP-V1 "Write" with the MM440 slot/index and the Y-link forwards it unchanged to the slave. There is no need for a GSD-XML or DD file beyond the standard PROFIdrive profile - the Drive ES plug-in already knows the MM440 parameter structure.

Method 3 - Direct DPV1 from STEP7 (No Drive ES)

If the customer does not license Drive ES, an alternative is to issue DP-V1 parameter read/write directly from the STEP7 program using SFB 52 / SFB 53 (RDREC / WRREC). This is heavier on the programmer but eliminates the Drive ES licence dependency.

Example - read MM440 parameter r0021 (actual frequency) over PROFIBUS DPV1:

// STEP7 STL, FB call in OB1
CALL  SFB 52 , DB52
  REQ   := M10.0
  IOID   := B#16#54            // output/input identifier
  LADDR  := W#16#0400          // MM440 logical base address (slot 0 in HW Config)
  RECNUM := B#16#01            // record number 1 -> parameter channel
  RET_VAL:= MW12
  BUSY   := M10.1
  RECORD := P#M 100.0 BYTE 10
  LEN    := MW14
  VALID  := M10.2
  ERROR  := M10.3
  STATUS := MW16

The parameter channel record layout (PNU request via PROFIdrive profile) is documented in Siemens FAQ 79607846. Writing back a saved parameter set is a write loop driven from a parameter table.

Verification After Replacement

Once the new MM440 has the parameter set, perform the following verification sequence before handing the drive back to production:

1. PROFIBUS diagnostics in STEP7: open HW Config, right-click the MM440, choose Diagnose -> Slave Diagnostics. The status must be "Station existing, no fault".
2. Cyclic I/O check: in Drive ES or STARTER, monitor PZD output (control word 1 = STW1) and PZD input (status word 1 = ZSW1). Toggle the on/off bit from the STEP7 program and verify ZSW1 bit 2 ("Operation enabled") rises.
3. Parameter spot-check: read P0700, P1000, P0918, P2103, P2200 against the offline backup. All values must match exactly.
4. Identification run (if motor data unknown): set P0010 = 1, P1900 = 2, then issue ON command via PROFIBUS. The drive performs an automatic motor identification; ZSW1 bit 10 indicates completion.
5. Save to EEPROM: confirm P0010 = 0 and either Drive ES "Copy RAM to ROM" was executed or P0010 = 30 -> set to 30 for 5 s -> revert to 0.
6. Power cycle test: remove 24 V control for 30 s, restore, verify parameters survived.

Troubleshooting Matrix

Y-Link Specific Constraints

Because the Y-link sits between the H-CPU and the MM440, two behaviours are important to understand:

• Bus failure on DP2 does not cause an H-CPU fail-over. The Y-link masks the lower segment's health from the redundant DP1. If all MM440 stations lose communication simultaneously, the H-system will not switch over - this is correct behaviour for an auxiliary bus, but it means the engineering workstation should still be on DP1 or on a separate PG cable to remain available during a Y-link fault.
• Y-link pair SWR and timer settings (SWR = 100, monitor = 100 ms typical) limit the number of acyclic DPV1 requests per second. Drive ES retries automatically, but a 5-drive fleet may take 60-90 s for a full upload. Increase SWR on the Y-link from 100 to 200 if diagnostics reports acyclic timeout.

Document References

• MM440 Operating Instructions: Siemens MM440 manual collection
• S7-400H System Manual: S7-400H documentation portal
• Y-link manual (DP/PA Link, Y-link): DP/PA-Link and Y-link manual
• Drive ES / STARTER commissioning guide: STARTER commissioning manual
• PROFIdrive profile (PNO): PROFIdrive Profile V4.2

FAQ