S7-400

A host of features support users in programming, commissioning and servicing the S7-400:

• High-speed instruction execution.
• User-friendly parameter assignment
• Human machine interfacing:
  User-friendly OCM services are already integrated into the operating system of the S7-400.
• Diagnostics functions and self-test:
  The intelligent diagnostics system of the CPUs continuously checks the functional capability of the system and registers faults and specific system events.
• Password protection.
• Mode selector.
• System functions.

The SIMATIC S7-400 complies with national and international standards:

• CE mark
• UL approval
• CSA approval or cULus approval
• FM approval
• ATEX approval
• C-Tick, EMC marking for Australia and New Zealand
• IEC 61131-2
• Marine approvals of the classification authorities
  • ABS (American Bureau of Shipping)
  • BV (Bureau Veritas)
  • DNV (Det Norske Veritas)
  • GL (Germanischer Lloyd)
  • LRS (Lloyds Register of shipping)
  • Class NK (Nippon Kaiji Kyokai)

For details, refer to Manual "S7-400 Automation System S7-400 Module Specifications".

Design

An S7-400 system is simple to construct with a modular design. One outstanding feature of the the S7-400 is its rugged operation without a fan, which enables the hot swapping of signal modules.

Its simple design makes the S7-400 flexible and service-friendly:

• Simple module mounting.
• Backplane bus integrated into the mounting racks.
• Simple module replacement, without risk of one module being confused with another
• Proven connection technology
• TOP Connect:
  Pre-assembled wiring with 1-core to 3-core connections and screw-type or spring-loaded terminals.
• Defined installation depth:
  All connections and connectors are recessed into the modules and protected cover flaps.
• Minimal slot rules

Communication

The CPUs and the communications processors support the following communication types:

• Process communication;
  for cyclic addressing of I/O modules (exchange of the process image) via a bus (AS-Interface, PROFIBUS DP or PROFINET). Process communication is called up from the cyclic execution levels
• Data communication;
  for data exchange between automation systems or between HMI stations
  and several automation systems. Data communication takes place cyclically or it is called from the user program via blocks on an event-driven basis.

Data communication

The SIMATIC S7-400 has different data communication mechanisms:

• Cyclic exchange of data packets between networked CPUs with global data communication (GD).
• Event-driven communication with partners via the communication functions

Networking can take place via MPI, PROFIBUS or PROFINET.

Global data (GD)

With the "Global data communication" service, networked CPUs can exchange data with each other cyclically via MPI (max. 16 GD packets, max. size of the GD packets 64 bytes per cycle). This allows, for example, one CPU to access the data/bit memories/process image of another CPU. If an S7-300 is networked, data exchange is restricted to a maximum of 22 bytes per packet. Global data communication can take place via the MPI. Configuring is carried out using the GD table in STEP 7. In the segmented CR2 mounting rack, two CPUs can communicate via the C bus using GD.

Communication functions

Communication services with S7/C7 partners can be established with system-integrated blocks.

The services are:

• S7 basic communication via MPI and PROFIBUS.
• S7 communication via MPI, C bus, PROFIBUS and PROFINET/Industrial Ethernet.

Communication services with S5 partners and non-Siemens devices can be established with reloadable blocks.

The services are:

• S5-compatible communication via PROFIBUS and Industrial Ethernet.
• Standard communication (non-Siemens systems) via PROFIBUS and Industrial Ethernet (Open User Communication over PROFINET/Industrial Ethernet).

In contrast to global data, communication connections must be set up for the communication functions.

Integration into the IT world

The S7-400 makes it possible to simply link the modern IT world with automation engineering. The following functions are possible using the plug-in CP 443-1 Advanced:

• Creation of your own web pages with any HTML tools. The process variables of the S7-400 are simply assigned to the HTML objects.
• Monitoring of the S7-400 via these Web pages using a standard browser.
• Sending of emails from the user program of the S7-400 via FC calls.
• Remote programming is possible due to the WAN characteristic of TCP/IP, even via the telephone network, e.g. ISDN.

The S7-400-H CPUs with PROFINET interface have integrated web servers. Information can thus be read out of the S7-400 station using a standard Web browser:

• General CPU information
• Content of the diagnostics buffer
• Variable table
• Tag status
• Module status
• Messages
• Information on Industrial Ethernet
• Diagnostics of the OUC connections
• Topology of the PROFINET nodes
• Display of process data and user data via user-defined web pages

Security mechanisms are available within the Web server mechanisms with the possibility of using user rights and supporting the HTTPS protocol.

Isochronous mode

The isochronous mode system function enables synchronous coupling to the cycle of the isochronous PROFIBUS and PROFINET for:

• Distributed signal acquisition
• Signal transmission
• Program execution

An automation solution is created that captures and processes the input signals and outputs output signals at constant intervals (constant bus cycle time). A consistent partial process image is created at the same time.

By means of constant bus cycle times and synchronous signal processing of the distributed I/O, the S7-400 ensures precisely reproducible and defined process response times.

An extensive range of components that support the isochronous mode system function is available for handling demanding tasks from the areas of motion control, measured value acquisition, high-speed controls, etc.

In distributed automation solutions, the SIMATIC S7-400 also opens up the important application area of high-speed processing operations and enables the achievement of maximum precision and reproducibility. This means increased production with optimal and constant quality.

Hardware configuration changes in RUN (Configuration in RUN, CiR)

With SIMATIC S7-400, hardware configuration changes can be made without reaction during operation of a plant. Options include:

• Addition of the distributed I/O nodes (PROFIBUS DP or PA slaves)
• Addition and re-parameterization of modules in the ET 200M I/O system.

CiR – Configuration in RUN reduces commissioning and retooling times by enabling plant expansions and conversions during the operating phase. In addition, this system functionality allows a flexible response to process changes (e.g. process optimization) since the plant does not have to be re-initialized or synchronized due to hardware configuration changes.

Diagnostics and process monitoring of modules

Many input/output modules of the SIMATIC S7-400 have intelligent abilities:

• Monitoring of signal acquisition (diagnostics)
• Monitoring of signals from the process (hardware interrupt)

Diagnostics

An intelligent diagnostics system can be used to determine whether signal acquisition (in the case of digital modules) or analog processing (in the case of analog modules) of the module is functioning fault-free. In diagnostics analysis, a distinction must be made between parameterizable and non-parameterizable diagnostics messages:

• Parameterizable diagnostics messages:
  The diagnostics message is only sent if it has been enabled by the appropriate parameterization.
• Non-parameterizable diagnostics message:
  These messages are sent as a matter of course, that is, independently of parameterization.

If a diagnostics message is active (e.g. "No sensor supply"), the module triggers a diagnostics interrupt (if the diagnostics message is parameterized, only after the appropriate parameterization). The CPU interrupts processing of the user program or low priority classes, and processes the relevant diagnostics interrupt block (OB 82). Process signals can be monitored via hardware interrupts and responses to changes in the signals can be triggered.

Different diagnostics messages are available depending on the module type:

Hardware interrupt

Process signals can be monitored, and responses to signal changes can be triggered via process interrupts.

• Digital input modules:
  Depending on the parameterization, the module can trigger a hardware interrupt for each channel group optionally at a rising edge, a falling edge or at both edges of a signal status change. The CPU interrupts processing of the user program or low priority classes, and processes the relevant process interrupt block (e.g. OB40). The signal module can buffer one interrupt per channel.
• Analog input modules:
  A working range is defined by parameterizing an high and low limit value. The module compares the digitized measured value with these limits. If the measured value violates one of these limits, a hardware interrupt is triggered. The CPU interrupts processing of the user program or low priority classes, and processes the relevant process interrupt block (e.g. OB40). If the limits are above/below the overrange/underrange, no comparison is made.

S7-400H

Fault-tolerant communication

With high-availability communication, SIMATIC offers the following features:

• Increased availability:
  In the event of a fault, communication can be continued via up to 4 redundant connections.
• Simple operation;
  high-availability is not apparent to the user. User programs for standard communication can be adopted without changes. The redundancy function is defined only at the parameterization stage.

Fault-tolerant communication is currently supported by the S7-400H (redundant and non-redundant configuration) and by PCs. On PCs, the Redconnect program package is required (see "SIMATIC NET communication systems").

Depending on availability requirements, different configuration options can be used:

• Single or redundant bus.
• Bus in linear or ring topology.

Mode of operation

The operating system of the CPU 417-5H/416‑5H/414‑5H/412‑5H executes all the necessary additional functions of the S7-400H autonomously:

• Data exchange
• Fault response (failover to standby device)
• Synchronization of both subunits
• Self-test

Redundancy principle

The S7-400H works according to the principle of active redundancy in "hot standby" mode (reaction-free automatic switchover in the event of a fault). According to this principle, both subunits are active during fault-free operation. In the event of a fault, the intact device assumes control of the process alone.

To guarantee this transfer bumplessly, fast and reliable data exchange via the central controller link is required.

In the course of the failover, the devices automatically retain:

• the same user program
• the same data blocks
• the same process image contents
• The same internal data such as timers, counters, bit memories, etc.

This means both devices are always completely up-to-date and can continue control alone in the event of a fault.

For redundant operation of the I/O, this results in the following:

• During fault-free operation, both modules are active, that is, in the case of redundant inputs, for example, the shared sensor (two sensors are also possible) is read in via two modules, and the results are compared and made available to the user as a unified value for further processing. In the case of redundant outputs, the value calculated by the user program is output by both modules.
• In the event of a fault, e.g. if one of the two input modules fails, the defective module is no longer addressed, the fault is signaled and processing continues with the intact module only. Following the repair that can take place online, both modules are again addressed.

Synchronization

For reaction-free switchover, synchronization of both subunits is necessary.

The S7-400H works with "event-drive synchronization".

This involves a synchronization operation whenever events could result in different internal states in the subunits, e.g. in the case of:

• Direct access to the I/O
• Interrupts, alarms
• Updating of the user times
• Modification of data by means of communication functions

The synchronization takes place automatically by means of the operating system and can be ignored at the programming stage.

Self-test

The S7-400H executes extensive self-tests. This involves testing the following:

• Connection of the central controllers
• Central processing units
• Processors/ASICs
• Memory

Every detected fault is reported.

Self-test at startup

At startup, each subunit executes all self-test functions fully.

Self-test in cyclic operation

The complete self-test is spread over several cycles. A short section of the self-test is executed per cycle so that the load on the actual controller is insignificant.

Configuring, programming

The S7-400H is programmed like an S7-400. All the STEP 7 functions available there are used.

STEP 7 V5.2 is required for programming the S7-400H.

Configuring of I/O modules

When configuring the hardware, users must specify via HW Config which modules are mutually redundant. This only requires the specification of the modules to be operated in redundant mode and the second module that is to be the "redundancy partner". In the user program, the module with the lowest address is to be accessed. The second address remains hidden from the user and programming of the control section with redundant and non-redundant I/O is identical. The only difference to non-redundant I/O are two FBs (RED_IN and RED_OUT) from the block library that are to be called at the start and at the end of the user program.

In STEP 7 V5.3 or higher, the library is integrated as standard into STEP 7.

S7-400H

The S7-400F/FH meets the following safety requirements:

• Requirement class AK 1 to AK 6 in accordance with DIN V 19250/DIN V VDE 0801
• Safety requirement class SIL 1 to SIL 3 in accordance with IEC 61508
• Category 1 to 4 in accordance with EN 954-1

Mode of operation

The safety functions of the S7-400F/FH are contained in the F program of the CPU and in the fail-safe signal modules.

The signal modules monitor output and input signals by means of discrepancy analyses and test signal injections.

The CPU checks the proper operation of the controller with regular self-tests, command tests, and logical and chronological program execution checks. In addition, the I/O is checked by means of sign-of-life requests.

If a fault is diagnosed in the system, the system is brought to a safe state.

F-Runtime license

The F-Runtime license must be loaded onto the CPU to operate the S7-400F/FH. One license is required for each S7-400F/FH.

Programming

The S7-400F/FH is programmed in the same way as the other SIMATIC S7 systems. The user program for non-fail-safe plant sections is created with proven programming tools such as STEP 7.

S7 F Systems optional package

The option package "S7 F Systems" is required for programming the safety-related program sections. The package contains all the functions and blocks required to create the F program.

For the F program with safety functions, special function blocks from the F library are called up with CFC and interconnected. The use of CFC simplifies the configuring and programming of the plant and, thanks to plant-wide, uniform representation, also the acceptance test. Programmers can concentrate fully on the safety-related application without having to use additional tools.