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| Place of Origin | GERMANY |
| Brand Name | SIMENS |
| Certification | CE RoHS |
| Model Number | 6ES7414-4HJ04--0AB0 |
The Siemens 6ES7414-4HJ04-0AB0 is the CPU 414H — one of the central processing units in the SIMATIC S7-400H high-availability controller family. Like all H-series CPUs, the 414H is designed to be deployed in pairs: two identical CPUs installed in two separate racks, connected through fibre-optic synchronisation cables via their sync interfaces, and running the same programme simultaneously in a hot-standby redundant configuration.
When one CPU fails, the partner takes over instantly — within a single scan cycle — with no interruption to the controlled process.
The 6ES7414-4HJ04-0AB0 sits at the entry point of the 414H memory range, offering 1.4MB total memory split equally between programme and data.
Compared to its successor in the same family (the 6ES7414-4HM14-0AB0, which doubles the memory to 2.8MB), the 4HJ04 variant is well-suited to process control programmes of moderate complexity — those with substantial PID loop management and alarm processing, but not requiring the very large programme and data structures of the largest continuous process automation applications.
The 4.5W power loss and 1.07kg weight reflect a compact, efficiently designed module — these figures matter in multi-rack S7-400 installations where many modules share a common cabinet and thermal management is a real engineering consideration.
At 4.5W, the CPU 414H's thermal contribution is modest even in a fully loaded rack.
| Parameter | Value |
|---|---|
| Total Memory | 1.4 MB (700KB data + 700KB program) |
| MPI/DP Interface | 1 × 12 Mbit/s RS-485 |
| DP Interface | 1 × 12 Mbit/s RS-485 |
| Sync Interfaces | 2 × (for IF 960 FO modules) |
| Power Loss | 4.5W typical |
| Dimensions (L×W×H) | 219×50×290mm |
| Weight | 1.07 kg |
| Compatible Systems | S7-400H, S7-400F/FH |
| Status | Discontinued spare |
The S7-400H platform offers multiple H-CPU variants, each stepping up in memory capacity to match the scale of the automation programme. The CPU 412H (6ES7412-3HJ14-0AB0) starts at 768KB total — suitable for smaller process units.
The CPU 414H at 1.4MB (this part) handles programmes of moderate size and complexity. The CPU 414H at 2.8MB (6ES7414-4HM14-0AB0) extends to larger continuous process control programmes. At the top, the CPU 417H variants reach up to 20MB for the most complex plant-wide automation programmes.
The 1.4MB memory split of the 4HJ04 — 700KB data and 700KB programme — reflects a balanced design philosophy. Process control programmes tend to generate larger data structures than equivalent machine control programmes, due to the extensive use of process data objects (PDOs), alarm tables, and historian buffers.
The equal 700KB/700KB split acknowledges this, providing substantial data memory alongside the programme memory.
For the application range the 414H targets — control of a process unit such as a distillation column, a reactor section, or a water treatment stage — 700KB of programme memory accommodates several hundred control loops, associated alarm logic, and communication handling with the SCADA layer.
The two PROFIBUS DP interfaces on the CPU 414H allow independent management of separate field device networks:
MPI/DP combined interface: Configurable as either MPI (for programming terminal and HMI connection) or PROFIBUS DP master. When configured as DP master, this interface manages one group of PROFIBUS field devices — for example, a PROFIBUS network dedicated to drives, variable-speed pumps, and motor starters.
Dedicated DP interface: Always operates as PROFIBUS DP master.
This interface manages a second, independent PROFIBUS network — for example, a network dedicated to instrumentation (pressure, flow, temperature transmitters) separate from the drive network.
Separating drives and instrumentation onto independent PROFIBUS segments is a common design practice in process automation.
Drive modules generate significant bus traffic (frequent speed and torque data updates) and can consume PROFIBUS bandwidth that slows the update rate for instrumentation.
Separate segments, each on its own DP master interface, isolate these traffic profiles and ensure both network types achieve their required update rates independently.
The two sync module interfaces accept pluggable IF 960 fibre-optic synchronisation submodules. These submodules connect to corresponding submodules in the partner CPU rack via fibre-optic cables, forming two independent, galvanically isolated synchronisation links between the two CPU racks.
Both CPU racks run the same programme simultaneously, synchronising their data at every scan cycle through the sync links.
If the active CPU detects a hardware fault, it signals the standby CPU to take over immediately — the standby CPU has all current data and continues execution without a restart.
From the field devices' perspective, the PROFIBUS cycles continue uninterrupted.
The two sync links are mandatory: if one sync link fails, the system continues operating but with degraded redundancy — one link maintains synchronisation while the fault alarm prompts maintenance to restore the second link before any process-critical event occurs.
Q1: How does the CPU 414H compare to the 412H, and how do I choose between them?
The CPU 412H has 768KB total memory with one MPI/DP interface and two sync interfaces — no dedicated second DP port. The CPU 414H has 1.4MB memory and adds a second dedicated PROFIBUS DP master interface.
Choose the 412H when the process control programme is compact and a single PROFIBUS network is sufficient.
Choose the 414H when either the programme needs more than ~640KB (leaving some margin) or when two independent PROFIBUS DP networks are required for large field device counts.
Q2: Can the CPU 414H operate in standard S7-400 (non-H) mode if only one unit is installed?
Yes. When only one CPU 414H is installed, or when the sync link between two CPUs is absent, the CPU operates in "single operation" mode — it runs the user programme and controls the PROFIBUS networks normally, without the redundancy function.
The CPU generates a diagnostic alarm indicating that full redundancy is not available.
All process control functions work normally; only the automatic failover protection is absent until the second CPU and sync links are restored.
Q3: Is STEP 7 the only programming environment, and is TIA Portal supported?
The CPU 414H is programmed with Siemens STEP 7 Professional V5.4 SP4 or later — the classic STEP 7 environment.
TIA Portal does not support the S7-400H CPU family for programming. Existing STEP 7 projects for S7-400H systems must remain in the STEP 7 environment for development and maintenance.
For new high-availability PLC projects, Siemens offers the S7-1500H as the current-generation TIA Portal-compatible replacement platform.
Q4: What replacing the 6ES7414-4HJ04-0AB0 in a running H-system — what procedure is required?
The S7-400H supports online CPU replacement while the partner CPU continues operating.
The replacement procedure: power off the rack containing the failed CPU, physically replace the CPU module, restore power to the rack — the replaced CPU synchronises with the still-running partner CPU through the sync links and re-enters hot-standby status automatically.
No programme download is required (the programme is in the running CPU's memory and is copied to the replacement during re-synchronisation).
Matching the firmware version of the replacement CPU to the running partner is recommended to ensure compatibility.
Q5: What is the migration path from the CPU 414H to a current Siemens platform?
Siemens recommends the SIMATIC S7-1500H as the successor platform. The S7-1500H CPUs (1513H-1 PN, 1517H-3 PN) provide comparable or superior high-availability redundancy with PROFINET-based field device networks, TIA Portal engineering, and significantly larger memory.
Migration involves hardware redesign (S7-1500 modules are not compatible with S7-400 racks), programme conversion from STEP 7 to TIA Portal (no automated code conversion — manual re-engineering is required), and network transition from PROFIBUS to PROFINET IO for field devices.
This is a capital project, typically executed during planned plant shutdown, and Siemens provides migration tools and engineering services to support the transition.
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