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Entry type: Product note Entry ID: 109762993, Entry date: 12/21/2018

Important information on SIMATIC S7-400H safety programs during uninterrupted operation

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If a safety program is used (SIMATIC S7 F system), an unscheduled stop may occur after more than 9 years of uninterrupted operation without resetting the CPU. The safety application is transferred into the defined safe state, in stand-alone or solo operation. If the CPUs are used redundantly, the system initially only switches to solo mode.

The H system may fail if the remaining CPU stops before redundancy is restored.
The described behavior does not occur any more from firmware version V6.0.7 of the H-CPUs and from firmware version V8.2.0 of the CPU 410. We recommend upgrading the CPUs to the current firmware version. If it is not possible to upgrade the firmware, the redundant CPU can be subsequently switched to the de-energized state (see below).

As part of our continuous quality monitoring of our products, the following behavior was noted with the SIMATIC S7- 400 H-CPUs with safety programs (SIMATIC S7 F Systems):

During the diversified processing of the safety program, an unscheduled reaction occurs in the timer system of the SIMATIC S7-400 H-CPUs after approx. 9 years and 5 months.
The safety functions of the H-CPUs respond as expected:

In stand-alone mode:

  • immediate stop of safety program
  • all outputs are switched to the safe state
  • the CPU then changes to the operating status "Defective"

In redundant mode:

  • the CPU affected then changes to the operating status "Defective".
  • the second CPU remains in RUN.

The following measures will immediately reset the timer system (and reset the 9 years and 5 months):

  • update firmware
  • deactivate power supply/supplies of the rack

In redundant systems, the subsystems can be deactivated one after the other for a short time so that at least one subsystem remains in operation.
Please also observe the notes on solo operation in the manual and make sure that there is no redundancy error before switching over.

The power supplies should be switched off and on again with a time delay (several hours apart) if a redundant system is affected, so that a sufficient reaction time remains in the case of a possible future uninterrupted operating period of more than 9 years.

Products affected

Discontinued or type-canceled H-CPUs:

All SIMATIC S7-400 H-CPUs of firmware version V1 .. V3:

  • 6ES7414-4HJ00-0AB0
  • 6ES7417-4HL00-0AB0
  • 6ES7417-4HL01-0AB0

 All SIMATIC S7-400 H-CPUs of firmware version V4:

  • 6ES7 414-4HJ04-0AB0 
  • 6ES7 417-4HL04-0AB0

All SIMATIC S7-400 H-CPUs of firmware version V4.5:

  • 6ES7 412-3HJ14-0AB0
  • 6ES7 414-4HM14-0AB0 
  • 6ES7 414-4HR14-0AB0
  • 6ES7 417-4HT14-0AB0

Current H-CPUs:

SIMATIC S7-400 H-CPUs up to firmware version V6.0.6:

  • 6ES7 412-5HK06-0AB0
  • 6ES7 414-5HM06-0AB0 
  • 6ES7 416-5HS06-0AB0
  • 6ES7 417-5HT06-0AB0

SIMATIC PCS 7-CPU 410 up to firmware version V8.1.3:

  • 6ES7410-5HX08-0AB0
  • 6ES7410-5HN08-0AB0

Not affected:

  • All SIMATIC S7-400 standard, PN and F-CPUs
  • All SIMATIC S7-400 H-CPUs or H-systems without safety program
  • SIMATIC S7-400 H-CPU as from V6.0.7 (see entry ID 109474550)
  • SIMATIC PCS 7-CPU 410 ab V8.2.0 (see entry ID 109476571)
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