ET200S Standalone PLC: IM 151-8 PN/DP CPU Configuration Guide

Overview: When an ET200S Becomes the Controller

The SIMATIC ET200S distributed I/O system is normally deployed as a Profibus or Profinet slave, fronted by an S7-300, S7-400, S7-1200, or S7-1500 CPU. For small machine control applications (typically 16 to 40 digital I/O points, one or two HMI panels, and a handful of variable frequency drives), the same rack can host an ET200S interface module with an integrated CPU. This standalone configuration eliminates a separate PLC rack, reduces panel space, and cuts hardware cost while still exposing the ET200S's wide I/O module catalog to the application.

This reference covers the three ET200S CPU variants that operate as a standalone PLC: the IM 151-7 (Profibus slave interface, S7-300 instruction set), the IM 151-8 PN/DP (Profinet device/Profibus master with S7-300 instruction set), and the IM 151-8F PN/DP F-CPU for safety-integrated applications. It also documents the supporting I/O, drive, HMI, and TIA Portal licensing decisions an engineer must make when building a system around 20 digital inputs, 20 digital outputs, two Profinet HMI touch panels, and three SINAMICS G120 or G110 inverters.

ET200S Standalone CPU Variants and Part Numbers

Siemens offers three interface module CPUs for the ET200S. All three install in slot 1 of the terminal module and behave as a S7-300 class CPU with a subset of the standard S7-300 work memory and instruction set. The differences are isolated to networking, work memory size, and functional safety support.

For the architecture described in the project (Profinet to two touch displays and three SINAMICS G120 / G110 inverters, no PROFIsafe requirement), the IM 151-8 PN/DP CPU (6ES7151-8AB01-0AB0) is the correct selection. It provides the integrated Profinet interface required to attach the HMI panels and G120 drives directly, and reserves the Profibus master channel for any future DP slaves.

Manual reference: SIMATIC ET 200S distributed I/O IM 151-8 PN/DP CPU interface module on the Siemens Industry Online Support (SIOS) portal.

ET200S vs S7-1200: Selecting the Right Platform for 20 In / 20 Out

An application with 20 digital inputs and 20 digital outputs is at the lower end of the S7-1200 family. The S7-1200 CPU 1214C ships with 14 DI / 10 DO onboard, so reaching 20/20 requires at least one SM 1223 or two SM modules, and a CPU 1214C DC/DC/DC or DC/DC/RLY as the head. A CP 1243-1 may be required if Profinet to G120 drives and HMI is needed (the 1214C's Profinet port is sufficient for the two HMI + three drives if MRP/MRP-client ring is not required).

Selection rule: choose the ET200S IM 151-8 PN/DP when the project expects future expansion to motor starters (ET200S PM-D Fx or DS1x-x), technology modules, or PROFIsafe. Choose the S7-1200 when total cost of ownership (including TIA Portal license) is the dominant constraint and the application will remain inside the S7-1200 hardware envelope.

ET200SP Controller Note

The ET200SP has a parallel lineup of "ET 200SP CPU" modules based on the S7-1500 instruction set (CPU 1510SP-1 PN, 1512SP-1 PN, 1515SP-2 PN, plus F-CPUs). These deliver higher performance, more work memory, OPC UA server, and Motion Control support not present in the S7-300-based ET200S. They are listed for reference only:

• SIMATIC ET 200SP Controllers (Siemens Product Page)

For the small, non-demanding, cost-driven project in the source, the ET200S IM 151-8 PN/DP is the right balance of cost and capability.

I/O Module Selection for 20 DI / 20 DO

ET200S digital I/O modules are catalogued by Siemens as 6ES7131-x (DI) and 6ES7132-x (DO). The 24 V DC variants pair with the standard PM-E 24 VDC power module in slot 0.

A typical 20 DI / 20 DO build uses three 8-channel DI modules (24 DI with spares) and three 8-channel DO modules (24 DO with spares) for a total of 7 ET200S slots plus the IM 151-8. If a 2-channel group fault diagnostic is required, upgrade to 6ES7131-6BF60-0BA0 (DI with diagnostics) and 6ES7132-6BF60-0BA0 (DO with diagnostics).

Slot Rules and Configuration in TIA Portal

Configuring an ET200S CPU in TIA Portal follows the slot rules documented for the ET200S station as a whole. According to the Siemens TIA Portal help (Configuring an ET 200S (S7-300, S7-400, S7-1500)):

1. Slot 1 must contain the IM 151-x CPU (no other module accepted).
2. Slots 2 through 63 accept power modules, digital/analog I/O, technology modules, and motor starters in any order, subject to backplane power budget.
3. A PM-E 24 VDC in slot 2 (or higher) is required to supply 24 V to the backplane and field side of subsequent modules.
4. Diagnostic interrupts from any module are routed to OB 82 and must be acknowledged in the user program if the diagnostic LED is to clear.
5. Module substitution is allowed when both the configured MLFB and the slot index match the physical install; otherwise, a station mismatch is reported and the CPU goes to STOP unless handled in OB 100 / OB 102.

When commissioning in TIA Portal, add the IM 151-8 PN/DP from the hardware catalog under Distributed I/O > ET200S > Interface modules > CPU IM 151-8 PN/DP. The catalog will not list the module under "PLCs > S7-300" — it is intentionally placed under the distributed I/O tree because the ET200S uses the S7-300 instruction set but slots as a distributed station.

Network Architecture: Two HMIs, Three VFDs on Profinet

The IM 151-8 PN/DP CPU acts as the Profinet I/O controller. The two touch displays (for example, KTP700 Basic PN, KTP1200 Basic PN) operate as Profinet I/O devices with the S7 communication protocol on the same subnet. The three G120 / G110 inverters with a SINAMICS G120 CU230P-2 PN or CU240E-2 PN Control Unit attach as Profinet devices and exchange process data on a configured PN cycle time of 1 ms to 4 ms.

Recommended IP plan for a single Profinet subnet:

The integrated 2-port switch on the IM 151-8 PN/DP eliminates an external managed switch for linear topology. Use a line topology for low cable cost or a star topology from a managed switch for serviceability.

SINAMICS G120 vs G120C Inverter Selection

For the 3 motors driving the application, the choice between G120 and G120C directly affects panel space and budget. The G120C is a compact, cabinet-mounted drive with the power module and Control Unit integrated in a single device; the G120 is a modular system with a separate power module (PM240 / PM240-2) and a plug-in Control Unit (CU230P-2 PN, CU240E-2 PN, CU250S-2 PN, etc.).

TIA Portal Licensing for ET200S IM 151-x

Unlike the S7-1200 (which ships with TIA Portal Basic), the ET200S IM 151-x CPU family requires TIA Portal Professional for offline/online configuration and programming. The license matrix is summarized as follows:

Project-Specific Bill of Material

The following BoM is a complete, orderable solution for the source application. Pricing varies by region and Siemens distribution channel; this list is for engineering reference only.

Programming Example: Scaling a G120 Setpoint in the IM 151-8

For a G120/G120C controlled over Profinet, the controller receives a Normalized Speed Setpoint (NSOLL) on word 0 of the Standard Telegram 1, scaled 0 to 0x4000 hex (0 to 16384 decimal) representing 0% to 100% of p2000 (rated speed). Use the following STL snippet to convert an integer percent (0 to 100) to the NSOLL format:

// Inputs: MW100 = setpoint percent (0..100)
// Output: MW110 = NSOLL A word 0 of PZD
L MW100              // Load percent
L 163                // Multiplier (100% × 16.38 to fit 0..16384)
*D                   // Result: 0..16300
ITD                  // Integer to double integer
T MD110              // Store as 32-bit word to drive PZD

For more accurate scaling, use the FC105 / FC106 scale blocks from the S7-300 library or the SCALE function block native to TIA Portal libraries.

Diagnostic and Error Handling

The IM 151-8 PN/DP supports diagnostic and process interrupts. Insert the following organization blocks in OB1 to handle fault scenarios:

Module diagnostics can also be read in the user program via SFC 51 (RDSYSST) and the SSL ID 0x00B4 (module diagnostic record). A complete diagnosis includes the channel, type (wire break, short circuit, no load, supply missing), and time stamp.

Troubleshooting Matrix

Commissioning Procedure

1. Wire the ET200S backplane. Place PM-E 24 VDC in slot 0, IM 151-8 PN/DP CPU in slot 1, then DI and DO modules in slots 2 through 7.
2. Connect a Profinet patch cable from a PC to the IM 151-8 PN/DP. Assign a temporary IP to the engineering station in the 192.168.0.x range.
3. In TIA Portal, create a new project, add the IM 151-8 PN/DP CPU via the hardware catalog (Hardware Catalog > Distributed I/O > ET200S > Interface modules > CPU IM 151-8 PN/DP). The catalog entry will only appear if the matching HSP is installed.
4. Configure the Profinet interface of the IM 151-8 as a Profinet IO controller. Add the two HMI panels and three G120C drives as IO devices and assign the IP / device names per the table above.
5. Assign IO cycles of 1 ms. Set the watchdog time to at least 3x the send clock (e.g., 3 ms watchdog for 1 ms send clock).
6. Configure the G120/G120C Standard Telegram 1 (PZD length 2/2) and download the SINAMICS parameters to each drive via the drive's commissioning wizard (STARTER, SINAMICS Startdrive, or Web server for G120C FW V4.7 SP10+).
7. Write the S7 program (or import from STEP 7 V5.5 if migrating). Compile, download HW config + SW to the IM 151-8, and run the CPU.
8. From the HMI, verify the HMI tags are bound to the correct PLC tag addresses (e.g., I0.0..I2.3 for DI, Q0.0..Q2.3 for DO, MW100 for VFD setpoint).
9. Run an I/O check: turn on each input, observe the corresponding bit in the HMI, then toggle each output from the HMI and confirm the field device responds.

Verification Checklist

• IM 151-8 RUN LED steady green, no SF/BF
• All 24 I/O modules show green "ready" LED on the front
• HMI 1 and HMI 2 can read all 20 DI states and write all 20 DO states
• Each G120C reports a Profinet "online" status and a healthy control word (control word 1 = 0x047E, status word 1 = 0x0B31 when running at zero speed)
• Diagnostic buffer of the IM 151-8 is free of errors after 30 minutes of run time
• HMI alarming is configured for wire break / short circuit at DO 8x24 VDC/0.5A channels (per MLFB 6ES7132-6BF60 if diagnostic DO is fitted)

Migration Note: From STEP 7 V5.5 to TIA Portal

If the engineer is moving from STEP 7 V5.5 (as mentioned in the source) to TIA Portal V17 or later, the IM 151-8 project can be migrated using the TIA Portal "Migrate project" function. The conversion preserves the hardware configuration, the symbol table, and the STL program. Note the following migration caveats:

• Libraries must be re-attached; the S7-300 library "Standard Library > IEC" becomes "Libraries > Standard Library > IEC" with a different absolute path.
• Any FBs using long STL sequences may require re-typing as SCL or as a GRAPH FB.
• HSM (Hot Swap Module) features are preserved but require the matching HSP for the target TIA Portal version.

Frequently Asked Questions