Siemens PLC Guide: LOGO!, S7-1200 and S7-1500 Compared

Siemens PLC hardware spans three tiers under the SIMATIC brand: LOGO! logic modules for simple automation, the S7-1200 compact controller for standard machine control, and the S7-1500 controller for complex, high-performance applications. All three trace back to the SIMATIC trademark Siemens registered in 1958 — a portmanteau of “Siemens” and “Automatic” — and today’s S7-1200 and S7-1500 controllers are programmed through the same TIA Portal software that also configures Siemens HMI panels and SINAMICS drives. Choosing the right Siemens PLC controller means matching I/O count, memory, and safety requirements to the machine, not defaulting to whichever model a catalogue lists first.

This guide walks through LOGO!, S7-1200, and S7-1500 side by side, covers the legacy S7-300 and S7-200 series still running in Malaysian factories, and closes with how Siemens PLC programming and HMI/VFD selection fit into the same TIA ecosystem.

Siemens SIMATIC PLC Overview

Siemens registered the SIMATIC trademark with the German Patent and Trademark Office on 2 April 1958. The programmable logic controller siemens line has gone through four major generations since: hard-wired relay replacements (Simatic G, then Simatic N on silicon transistors), the first microprocessor-based Simatic S3 in 1973, the Simatic S5 series from 1979 to 2000, and the current Simatic S7 generation launched in 1994.

Every current Siemens SIMATIC PLC controller sits inside the S7 family: S7-1200 and S7-1500 for new installations, with S7-300, S7-400, and S7-200 still running in older Malaysian production lines. LOGO! sits outside the S7 numbering entirely — a separate logic-module line for automation tasks too simple to justify a full PLC controller. The sections below cover each of these in turn, starting with LOGO! at the entry point of the range.

Siemens PLC LOGO! — Logic Module Basics

Siemens PLC LOGO! is a logic-module line, separate from the SIMATIC S7 controller family, positioned for straightforward tasks rather than full production-line automation. Siemens positions the current LOGO! 9 generation as “Logic Modules for Everyday Automation, connected, scalable and simple” — placing it below the S7 controllers for straightforward control tasks such as lighting, pumps, gates, and small machine sequences rather than full production-line automation. Because it sits at the entry point of the range, Flextech Industrial classifies LOGO! within the micro/nano PLC pricing tier (roughly RM 600–2,500) rather than alongside the compact or modular S7 controllers.

LOGO! is not part of the Simatic S7 architecture and is documented separately from it. When an installation needs a full graphical operator interface beyond basic on-module status indication, that’s the point where a standalone Siemens HMI panel — configured through the WinCC package inside TIA Portal — becomes worth specifying instead. This distinction between a logic module’s built-in indication and a dedicated HMI panel matters when a Malaysian system integrator is deciding whether “hmi logo” needs actually call for a separate panel or not; the next sections on S7-1200 and S7-1500 assume that decision has already pointed toward a full PLC controller rather than a logic module.

Siemens PLC S7-1200 — Compact Controller

The S7-1200 is Siemens’ compact PLC controller for standard machine control, launched in April 2009 to replace the S7-200 series. A plc siemens s7 1200 CPU unit measures approximately 100 mm × 75 mm, with up to 150 kB of working memory, 2 MB of integrated program memory expandable to 24 MB, and a bit-instruction execution time of roughly 0.1 μs. Communication runs over integrated Profinet and Ethernet interfaces, and programming is done in TIA Portal using the STEP 7 software package. Program storage sits internally on EEPROM or on a Simatic Memory Card (SD card).

Failsafe variants — CPU 1212FC, 1214FC, and 1215FC — add integrated safety I/O for applications where functional safety matters alongside standard control.

Siemens introduced a second generation, the S7-1200 G2, at Hannover Messe 2024, launching it commercially in December 2024–January 2025 alongside TIA Portal V20. The G2 modules are not hardware-compatible with first-generation units. Compared with the original S7-1200, the G2 line adds reduced execution time, support for Profinet Real-Time (RT) and Isochronous Real-Time (IRT) communication, Media Redundancy Protocol (MRP) and MRPD support, program memory up to 300 kB with working memory up to 8 MB, and compatibility with SIMATIC Motion Library technology objects. Early G2 units shipped with Near Field Communication (NFC) for phone-based diagnostics, though Siemens deactivated the NFC interface in a firmware update released a few months after launch.

Siemens PLC S7-1500 — Controller for Complex Automation

The S7-1500 is Siemens’ controller for complex, high-performance automation, presented at the SPS/IPC/DRIVES trade fair in Nuremberg in 2012 and brought to market in 2013 to gradually replace the S7-300 and S7-400 series. A plc siemens s7-1500 CPU integrates motion control as a standard function on every unit; only extended kinematics functions require the dedicated S7-1500T variant. Functional safety is available through failsafe S7-1500F CPUs, rated up to SIL3 per IEC 62061 and PL-e per ISO 13849. Every S7-1500 CPU ships with a Profinet interface, an integrated web server, and a colour display as standard, and the rack can expand to 32 modules.

Redundant R/H variants add dual central units with paired I/O for extended availability, and SIPLUS-branded versions extend most modules for extreme temperature and vibration. Siemens also offers the S7-1500V — an entirely virtual PLC that Siemens describes as delivering “familiar S7-1500 functions independent of hardware for greater flexibility and efficiency,” running as a Simatic CPU inside a Docker container under a Linux-based Siemens Industrial OS since 2023.

Summary So Far — LOGO!, S7-1200, and S7-1500

LOGO! covers simple, standalone control tasks and sits outside the S7 numbering entirely. The S7-1200, launched in 2009, handles standard machine control with up to 150 kB of working memory and a compact form factor, with a second generation (G2) adding faster execution and larger memory since December 2024. The S7-1500, launched in 2013, steps up to integrated motion control, SIL3-rated safety variants, an integrated web server and colour display, and a rack that expands to 32 modules. All three are Siemens PLC options; the difference is scale and built-in capability, not brand.

LOGO! vs S7-1200 vs S7-1500 — Which Siemens PLC Fits

Five factors separate the three product lines in practice: typical role, product family, failsafe availability, motion control, and Flextech’s Malaysian pricing tier.

Reading straight down this table gives the practical decision rule: pick LOGO! when the entire control task is a handful of inputs driving a handful of outputs and no PLC-grade programming environment is needed; pick S7-1200 when the machine needs real I/O counts, Profinet networking, and TIA Portal programming without the cost of integrated motion or failsafe hardware; pick S7-1500 when the line needs built-in motion control, SIL-rated safety, or the headroom of a modular rack that can grow past 32 modules.

Legacy Siemens PLC — S7-300 and S7-200 Status

Siemens launched the S7-300 in 1994 alongside the S7-200 and S7-400, as one of three original performance classes in the S7 line. A plc siemens s7-300 CPU is a modular system — some compact variants include integrated I/O — communicating via integrated MPI, Profibus, Profinet, and Ethernet interfaces depending on the variant, with program storage on an MMC card and programming done through the standalone STEP 7 package (not the later TIA Portal). Memory ranges from 32 KB on the CPU 312 up to 2 MB on the CPU 319-3 PN/DP. A safety-rated S7-300F variant reaches SIL 1 to SIL 3 per IEC 61508. Wikipedia’s Simatic entry notes that Siemens expects to phase out the S7-300 and S7-400 series by 2033.

The siemens plc s7 200 series, by contrast, is already discontinued — Siemens ended sales in July 2017. S7-200 units were small (80 mm × 62 mm), fast (0.22 μs binary execution time), and programmed through the separate STEP 7 MicroWin software rather than STEP 7 or TIA Portal. Even though it’s no longer sold as a standalone product, the S7-200 architecture continues to turn up in Malaysian metalworking shops because it’s still integrated inside the Sinumerik 828D CNC control system. The S7-1200, launched in 2009, is what replaced the S7-200 as Siemens’ compact-PLC entry point going forward.

Siemens PLC Programming — Software and Languages

Every current S7-1200 and S7-1500 controller is programmed through TIA Portal (Totally Integrated Automation Portal). Siemens released the first version as STEP 7 Basic V10.5 in April 2009, covering the S7-1200 only; TIA Portal V11 in 2011 extended coverage to the S7-1200, S7-300, and S7-400; and TIA Portal V12 in 2013 added support for the newly launched S7-1500. Plc programming siemens today follows the IEC 61131-3 standard languages inside TIA Portal: LAD (ladder logic, similar to an electrical circuit diagram), FBD (function block diagram, similar to a logic-gate diagram), SCL (a Pascal-based structured text language for complex logic such as REPEAT-UNTIL and CASE structures), and Graph/SFC for sequential control built from steps and transitions. STL, a low-level instruction-list language, remains available mainly for migrating older S7-300/400 projects.

The legacy S7-300 and S7-400 series were originally programmed through the standalone STEP 7 package rather than TIA Portal, while the discontinued S7-200 used the separate STEP 7 MicroWin software. That software split — one package for legacy hardware, TIA Portal for S7-1200/S7-1500 — is one practical reason Malaysian integrators standardise new projects on the S7-1200 or S7-1500 rather than adding a second licence to support an ageing S7-300 line.

Siemens HMI and Siemens VFD — Completing the Automation Layer

A Siemens PLC controller rarely runs a machine on its own — most installations pair it with an HMI panel for operator interaction and a VFD for motor speed control, both configured from the same TIA Portal engineering environment as the PLC program itself. Hmi siemens panels are engineered through the WinCC package, which spans the Basic, Comfort, Advanced, and Professional tiers as well as WinCC Unified — a distinct HMI engineering system Siemens introduced within TIA Portal starting with version 16 in 2019.

On the drive side, a siemens vfd is parameterised inside TIA Portal through the StartDrive package rather than a separate programming tool, keeping the PLC program, HMI screens, and drive parameters in one project. TIA Portal’s release history shows StartDrive gaining support for current SINAMICS drive families — including the S200, S210, and G220 — as recently as the 2023 TIA Portal update, alongside the same S7-1200/S7-1500 controller support already covered above.

For a Malaysian system integrator specifying a full production line, keeping the Siemens PLC controller, HMI panel, and VFD on one TIA Portal project simplifies commissioning even when the parts are sourced from a single PLC supplier rather than several. Flextech Industrial’s inverter category and HMI category cover the drive and panel side of that same automation layer. For help matching a specific model to an existing production line, Flextech Industrial’s team can advise on Siemens PLC, HMI, and VFD selection across Selangor, Penang, and Johor.

Frequently Asked Questions

Programming software and legacy status cover the technical planning side of a Siemens PLC purchase; these six questions cover the recurring points that come up when a Malaysian integrator is comparing LOGO!, S7-1200, and S7-1500 side by side.

What is a Siemens PLC controller used for?

A Siemens PLC controller separates a machine’s control logic from its physical operation, reading sensor inputs and driving actuator outputs in real time according to a stored program. Siemens sells this hardware under the SIMATIC S7 brand — S7-1200 for standard machine control, S7-1500 for complex or high-availability lines, and the legacy S7-300/S7-400/S7-200 series in older installations.

What is the difference between Siemens S7-1200 and S7-1500?

The S7-1200, launched in 2009, is a compact controller with up to 150 kB of working memory, aimed at standard machine control. The S7-1500, launched in 2013, integrates motion control as standard on every CPU, offers failsafe variants up to SIL3, ships with an integrated web server and colour display, and expands to 32 modules — putting it a tier above the S7-1200 for complex or high-performance automation.

Is Siemens LOGO! a PLC?

Siemens documents LOGO! as a logic module line, separate from the SIMATIC S7 PLC controller family it sits alongside. It performs a similar role — reading inputs and driving outputs to a stored logic sequence — but at a smaller scale intended for simple automation tasks like lighting or pump control rather than full production-line automation.

What software is used for Siemens PLC programming?

Current S7-1200 and S7-1500 controllers are programmed in TIA Portal, using IEC 61131-3 languages such as LAD, FBD, and SCL. The legacy S7-300 and S7-400 series use the standalone STEP 7 package, and the discontinued S7-200 series used STEP 7 MicroWin — a different software package from either.

Is Siemens S7-300 still available?

Siemens continues to sell the S7-300, though Wikipedia’s Simatic entry notes an expected phase-out by 2033 as the S7-1500 gradually takes over its role. The S7-200 predecessor is already discontinued as of July 2017, though S7-200 hardware remains embedded inside the Sinumerik 828D CNC control system.

Does Siemens make HMI panels?

Yes — Siemens HMI panels are engineered through the WinCC package inside TIA Portal, spanning Basic, Comfort, Advanced, and Professional tiers, plus the newer WinCC Unified engineering system introduced in TIA Portal V16 in 2019. The same TIA Portal project can configure the HMI panel, the S7-1200/S7-1500 PLC program, and a SINAMICS VFD together.