Simulating SIMATIC FM 458-1 DP High-Speed Controllers in SIMIT V9.1

The SIMATIC FM 458-1 DP application module (6DD1607-0CA1) cannot be simulated purely in software using the SIMIT Virtual Controller (VC) or S7-PLCSIM in SIMIT V9.1. Because the FM 458-1 DP features a dedicated 64-bit RISC processor executing sub-millisecond control algorithms compiled under D7-SYS and STRUC, its microcode architecture is outside standard S7 CPU emulation. To validate FM 458-1 DP application software within a SIMIT simulation environment, a Hardware-in-the-Loop (HIL) topology must be deployed. In this architecture, physical FM 458-1 DP hardware is mounted in an S7-400 rack while a SIMIT UNIT interface device emulates the connected PROFIBUS-DP and PROFINET field devices, enabling real-time, reaction-free testing of high-speed drives and motion control loops.

FM 458-1 DP Architecture and Simulation Boundaries

The FM 458-1 DP (6DD1607-0CA1) is an advanced function module engineered for applications requiring microsecond-range cycle times, such as metal rolling mill tension controls, winders, rotary shears, high-speed electronic cams, and cross-cutters. Unlike standard S7-400 central processing units, the module operates under the SIMATIC D7-SYS programming package:

Processor: Dedicated 64-bit RISC CPU (running at 264 MHz).
Execution Cycles: Configurable down to 0.1 ms (100 microseconds).
Software Runtime: Proprietary D7-SYS real-time executive, utilizing function block libraries compiled via ANSI-C.

Because standard software emulators—including S7-PLCSIM, S7-PLCSIM Advanced, and SIMIT Virtual Controller—are designed to emulate standard S7 Step 7 instruction lists (AWL/SCL/CFC) for S7-300, S7-400, and S7-1500, they lack the emulation kernel required for D7-SYS microcode.

Software-in-the-Loop vs Hardware-in-the-Loop

The following table compares Software-in-the-Loop (SIL) constraints against Hardware-in-the-Loop (HIL) capabilities:

| Evaluation Criterion | Software-in-the-Loop (SIL / SIMIT VC) | Hardware-in-the-Loop (HIL via SIMIT UNIT) |
|---|---|---|---|
| FM 458 Controller Hardware | None (Attempted software emulation) | Physical FM 458-1 DP in S7-400 subrack |
| Supported by SIMIT V9.1? | No (D7-SYS instruction set unsupported) | Yes (Standard certified Siemens method) |
| Field Devices (Drives/IO) | Simulated in SIMIT workspace | Emulated by SIMIT UNIT PB/PN hardware |
| Fieldbus Interfaces | Virtual software coupling | Physical PROFIBUS-DP / PROFINET cabling |
| Timing Fidelity | Non-real-time / best effort | Deterministic sub-millisecond real-time response |

Implementing SIMIT UNIT Field Device Emulation

To integrate the physical FM 458-1 DP with SIMIT V9.1, field devices are emulated using a SIMIT UNIT box:

Equipment Schedule

Simulation Hardware Components:
- SIMIT UNIT PB (PROFIBUS Interface Box):       6DL8900-0AK00-0AB0
  (Or SIMIT UNIT PN for PROFINET IO:             6DL8900-0AK10-0AB0)
- Controller Subrack Module:
  - SIMATIC FM 458-1 DP Application Module:      6DD1607-0CA1
  - SIMATIC S7-400 Universal Rack (UR2 / CR3):   6ES7400-1JA01-0AA0
  - SIMATIC S7-400 Power Supply (PS 407 10A):    6ES7407-0KA02-0AA0

Engineering Workflow

Export Fieldbus Configuration: In STEP 7 / HW Config, export the system configuration containing the FM 458-1 DP PROFIBUS-DP master line and connected drive slaves (e.g., SINAMICS S120, MASTERDRIVES).
Import into SIMIT: In SIMIT V9.1, navigate to Couplings -> New Coupling -> select SIMIT UNIT.
Import the HW Config export file (*.cfg or station XML). SIMIT automatically builds the address map of input/output process images for all configured field slaves.
Physical Interconnection: Connect standard PROFIBUS cables between the DP master port on the front of the FM 458-1 DP and the DB9 channel connector on the front panel of the SIMIT UNIT PB.
Connect the SIMIT UNIT management Ethernet port to the SIMIT engineering PC network adapter.
In SIMIT, assign simulation behavioral models (motors, mechanical loads, tension sensors) to the I/O signals.

Verification

To verify the FM 458-1 DP Hardware-in-the-Loop simulation:

Power up the S7-400 rack hosting the FM 458-1 DP module.
In SIMIT V9.1, verify that the SIMIT UNIT coupling status displays green with communication state Active.
Inspect the diagnostic LEDs on the front of the FM 458-1 DP:
- RUN LED: Solid Green (D7-SYS program actively executing cyclic tasks).
- IF_FLT / BF (Bus Fault) LED: Extinguished (confirms that SIMIT UNIT is successfully answering all PROFIBUS master polling cycles as legitimate field slaves).
In SIMIT, inject a speed reference or load perturbation into the virtual process model.
In D7-SYS Online Test / CFC, verify that the FM 458-1 DP reads the simulated feedback in real time and computes corresponding torque/speed manipulated outputs without timing jitter or fieldbus timeout errors.

Limitations and Operational Precautions

Operational boundaries when simulating FM 458 systems:

High-Speed Onboard I/O Simulation: The FM 458-1 DP expansion module EXM 438-1 (6DD1607-0CA2) features high-speed direct digital and analog inputs (sampled down to 10 microseconds) and incremental encoder inputs. These direct onboard electrical inputs cannot be emulated via fieldbus packets over SIMIT UNIT; they require physical signal generator hardware or test injection fixtures.
Hardware Requirement Mandatory: Engineering teams cannot perform virtual commissioning of D7-SYS motion programs purely in an office laptop environment without physical FM 458 hardware and a SIMIT UNIT box.
PROFIBUS Baud Rate Constraints: Ensure the configured baud rate in HW Config (typically 1.5 Mbps to 12 Mbps) matches the SIMIT UNIT hardware channel capability.

Engineer FAQ

Can S7-PLCSIM Advanced emulate the FM 458-1 DP?

No. S7-PLCSIM Advanced only emulates SIMATIC S7-1500 and ET 200SP Open Controllers. It has no capability to execute S7-400 hardware or D7-SYS modules.

What is the maximum number of fieldbus slaves a SIMIT UNIT PB can emulate?

A single SIMIT UNIT PB can emulate up to 125 PROFIBUS-DP slaves across its communication channels with 1 ms cycle resolution, fully satisfying large-scale industrial drive lineups.

Is SIMIT VC suitable for simulating other modules in the same rack?

Yes. If the S7-400 rack contains a standard CPU (such as CPU 416-3 or AS 410-5H) alongside the FM 458-1 DP, the main CPU can be emulated using SIMIT Virtual Controller, while the FM 458-1 DP runs on physical hardware connected via SIMIT UNIT.

Does SIMIT V9.1 require a specific license to interface with SIMIT UNIT?

Yes. Operating a SIMIT UNIT coupling requires the SIMIT Engineering license (SIMIT M, L, or XL) along with the corresponding communication driver configuration included in the base package.