S7 Hardware Configuration in TIA Portal: Complete Setup Guide

Configuring the hardware of a SIMATIC S7 controller in TIA Portal is more than just dropping a CPU and a few signal modules into a project. Every backplane-bound module — the CPU, the interface modules, the signal modules, the function modules, and the communication processors — must be represented in the device view with the exact order number (MLFB) that is installed in the cabinet. The power supply, mounting rail, and front connectors, while often physically decoupled from the backplane, still need to be selected so the bill of materials, the cabinet layout, and the spare-parts list stay consistent with what is actually wired on site.

This reference walks through the complete configuration flow: opening the device view, populating the rack with the correct PS, CPU, IM, SM, FM, and CP modules, integrating mechanical components (rails, front connectors, U-connectors), validating the configuration against the hardware catalog, and resolving the most common inconsistencies that appear at compile time.

1. S7 System Families and Their Hardware Variants

Before configuring, identify which S7 family the target installation uses. Each family has its own module series, firmware behavior, and rack rules. Mixing modules across families is not supported.

The remainder of this guide uses the S7-300 as the primary example because it is the family that most often raises the question "why does the device view only show the CPU and not the PS or rack?" — a result of the S7-300's segmented backplane where the PS does not occupy a slot in the device view in the same way it does on the S7-1500.

2. Prerequisites

Before opening the device view, gather the following so the configuration can be done in one pass without catalog lookups for every slot.

1. TIA Portal installation — V15.1, V16, V17, V18, or V19. Each major version expands the supported module catalog. Use the latest Siemens Industry Online Support HSP (Hardware Support Package) for the installed TIA Portal version so the catalog reflects the current MLFBs.
2. Module list with MLFBs — every backplane-bound module that is physically installed, including the firmware version if it is non-default.
3. Mounting rail length and order number — S7-300 rails are ordered by length (e.g., 160 mm, 482 mm, 530 mm, 830 mm, 2000 mm) with the MLFB prefix 6ES7 390-1....
4. Front connector type for each SM/FM — screw-type 20-pin (6ES7 392-1AJ00-0AA0), spring-type 20-pin (6ES7 392-1BJ00-0AA0), or 40-pin for S7-300 high-density modules.
5. Power supply order number — PS 305/307 for S7-300; PS 405/407 for S7-400; system PS or load PM for S7-1500.
6. Interface module (IM) order numbers — for multi-rack S7-300, the send IM (IM 360), the receive IM (IM 361), and the appropriate connecting cable (e.g., 6ES7 368-3BB00-0AA0 for 1 m).

3. Opening the TIA Portal Device View

The device view is the graphical representation of the rack and is the only place where the configured hardware must match the physical hardware. Open it with Project tree → Devices & networks → [PLC] → Device view.

The device view shows the rack as a horizontal strip of numbered slots. The exact slot count depends on the family:

• S7-300 — Slot 1 is reserved for the PS (or remains empty if the PS is mounted externally). Slot 2 is reserved for the CPU. Slots 3 to 8 hold signal/function/communication modules. Slot 9 is reserved for an IM 360 (send) in expansion rack 0.
• S7-400 — Slots are lettered and numbered (e.g., slot 1 power supply, slots 2-18 plug-in modules). The CR2 rack has two segments separated by a fan; each segment has its own PS slot.
• S7-1500 — Slot 0 is the system power supply; slot 1 is the CPU; slots 2-31 are I/O modules. A load PM can be added at the end.

If the device view is empty, double-click Add new device in the project tree and select the CPU from the catalog. The empty rack appears after the CPU is added.

4. Adding the Power Supply (PS) Module

For S7-300, the PS does not appear in the backplane in the same way the CPU does. It feeds the backplane via the bus connector and the wiring on the rail, but it has no logical module identity on the network. There are two consequences:

1. The PS does not occupy a numbered logical slot in the device view for S7-300. It is, however, present in the catalog and can be dragged to the rack outline as a visual reference.
2. The PS must be specified in the bill of materials separately. Use the TIA Selection Tool at siemens.com / tia-selection-tool to size and order the PS.

For S7-1500, the system PS is a real module in slot 0 of the device view and supplies the backplane. The load PM (PM 70W, PM 190W) is added to the right of the I/O modules and supplies the 24 V load circuit. Both are configured in the device view.

4.1 Sizing the power supply

The S7-300 PS 307 (e.g., 6ES7 307-1EA01-0AA0, 5 A) must supply both the backplane current and the 24 V sensor/actuator load. Use the formula:

I_PS >= sum(I_backplane) + sum(I_24V_load) + I_reserve

Typical S7-300 backplane currents for sizing:

Add 20 % reserve as a field-proven sizing margin. If the calculated load exceeds the smallest PS 307 (2 A), step up to the 5 A or 10 A variant.

5. Adding the CPU

The CPU is the only module that must match the physical hardware. Selecting the wrong CPU MLFB in the device view results in compile errors and incorrect address assignment.

1. In the device catalog (right-hand pane), navigate to Controllers → SIMATIC S7-300 → CPU.
2. Expand the family that matches the installed CPU (e.g., CPU 315-2 PN/DP).
3. Select the exact MLFB. The 6ES7 315-2EH14-0AB0 is a different firmware (V3.3) from the 6ES7 315-2EH13-0AB0 (V3.2) — confirm the label on the physical module.
4. Drag the CPU to slot 2 of the rack outline.

If the catalog does not list the CPU MLFB, install the matching Hardware Support Package (HSP) from Siemens Industry Online Support and re-open the device view.

6. Adding Interface Modules (IM) for Multi-Rack S7-300

An S7-300 with more than eight signal modules requires an expansion rack. Expansion racks connect through IM modules and dedicated cables. The rules are strict:

In the TIA Portal device view, drag the IM 360 to slot 9 of the central rack, then add a new Device → SIMATIC S7-300 → IM 361 device for the expansion rack. Connect them with a PROFIBUS or backplane bus link — for S7-300 IM 360/361, this is a dedicated IM connecting cable, not PROFIBUS. The cable length is selectable (1 m, 2.5 m, 5 m, 10 m).

7. Adding Signal Modules (SM)

Signal modules — digital input (DI), digital output (DO), analog input (AI), analog output (AO) — are added to the slots immediately to the right of the CPU. The order in the device view determines the I/O address assignment: slot 3 starts at byte 0 by default, slot 4 at byte 4, and so on.

1. Drag each SM to the device view, slot 3 onward.
2. Confirm the address assignment in Properties → I/O addresses. The default is fine for new projects; rewrite it only when aligning with an existing PLC program or HMI tag list.
3. For analog modules, open the Properties → Channels tab and set the measurement type (voltage, current 4-20 mA, RTD, thermocouple) and the diagnostic enable bits. Mismatches here are the most common cause of "value = 7FFF_H" (overflow) or "value = 8000_H" (wire break on S7-300 AI) in the user program.

8. Adding Function Modules (FM) and Communication Processors (CP)

Function modules (FM 350-1, FM 351, FM 352, FM 353, FM 354, FM 355, FM 357-2) handle high-speed counting, positioning, and PID tasks independently of the CPU scan. Communication processors (CP 340, CP 341, CP 342-5, CP 343-1 Lean, CP 343-1, CP 443-1, CP 443-5 Extended) handle fieldbus and industrial Ethernet connections that the CPU's built-in interface does not support, or for which offloading the communication is desired.

Each FM and CP is added to a free slot, in the same way as an SM. The device configuration in TIA Portal only describes the physical presence — the FM/CP firmware parameters (e.g., measuring range for FM 350, baud rate for CP 340) are configured in a separate dialog opened from the module's properties or via the FM-specific configuration tool launched from TIA Portal.

9. Mounting Rail Selection

The mounting rail is the mechanical foundation. For S7-300, the standard rail is 530 mm (6ES7 390-1AF30-0AA0), which holds the PS, CPU, and up to six SM/FM/CP modules. A longer 830 mm rail is required when the rack contains eight modules plus the PS.

Order the rail in the same tool as the modules — typically the TIA Selection Tool or the Siemens Industry Mall. The TIA Selection Tool calculates the rail length automatically once the slot list is finalized.

10. Front Connector Selection

Every S7-300 SM/FM uses a 20-pin or 40-pin front connector. The connector is mechanically keyed to the module and is not part of the backplane. The three common variants are:

Order one connector per slot occupied by an SM or FM. A spare connector for each type is a sensible spare-parts entry.

11. Using the TIA Selection Tool for a Complete Bill of Materials

The TIA Selection Tool (TST) is a browser-based configurator that produces a complete, exportable bill of materials including PS, rail, front connectors, and even labeling strips. It is the recommended way to size a cabinet before the device view is opened in TIA Portal.

1. Open the TST at siemens.com / tia-selection-tool.
2. Create a new project. Drag the controller, then the I/O modules, then the PS.
3. When the slot list is complete, switch to the Accessories tab. The TST proposes the correct rail length, the correct number of front connectors, and any U-connectors required between physically separated slots (S7-300 rule: a maximum of one slot gap is allowed between powered modules; gaps beyond that require a U-connector or a new power segment).
4. Export the bill of materials as CSV or transfer it to the Siemens Industry Mall shopping cart.

12. U-Connector and Backplane Continuity Rules (S7-300)

The S7-300 backplane is not continuous. The bus connector is built into each module, and the modules must sit on the rail in physical contact. If slots are left empty, the backplane is broken at that point. The S7-300 hardware rule is:

Slots 3 through 8 are powered by the CPU's backplane supply. If a slot is left empty, the modules to the right of the gap may not be powered. Use a dummy module (6ES7 370-0AA01-0AA0) or a U-connector to bridge the gap.

This is one of the most frequent field installation issues. A module physically mounted in slot 6, with slot 5 left empty, will not communicate — the backplane is broken at the empty slot. The TIA Portal device view does not enforce this; only the physical assembly does.

13. Verifying the Configuration

After populating the device view, run the following checks before downloading to the CPU.

1. Compile the hardware — Project tree → PLC → Compile → Hardware (rebuild all). Any inconsistency appears in the Inspector window under Info → Compile.
2. Compare online/offline — once the CPU is online, right-click the device and select Compare offline/online. The order number, firmware version, slot, and address of every module must match. Mismatches are highlighted in red.
3. Diagnostic buffer readout — open Online & diagnostics → Diagnostic buffer. Event ID 0x1394 (module pulled/plugged) confirms the physical module identity. Event ID 0x13A1 (module parameter assignment error) indicates that the configured channel type does not match the wiring.
4. I/O check — force a value at one DO and read back the corresponding input state at the cabinet terminals. This catches U-connector and addressing errors that the diagnostic buffer may not surface.

14. Troubleshooting Matrix

15. Field-Engineering Notes

• Spare part discipline. A 10 % spare population for each SM type, one spare PS, one spare front connector per type, and a 2 000 mm raw rail are field-proven defaults for an S7-300 cabinet.
• Firmware pinning. When a CPU firmware upgrade is performed in TIA Portal, every module in the device view may need to be re-pinned to the new firmware. TIA Portal V17 and later will warn about a non-uniform firmware configuration during compile.
• Project archival. Archive the configured project with the matching HSP list noted. A new install of TIA Portal without the same HSPs will open the project but show a stripped-down catalog and may not be able to download to the physical CPU without a catalog refresh.
• Labeling. Use the TST-generated labeling strips (e.g., 6ES7 392-2XX00-0AA0) for slot numbers. This reduces commissioning time and the chance of addressing mistakes during field wiring.

FAQ