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Entry type: Application example Entry ID: 23780904, Entry date: 03/22/2018
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Fast archiving of process data in SIMATIC PCS 7 with AR_SEND

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The SIMATIC PCS 7 process control system has the functionality of transferring process values from an automation system (AS) to a process value archive of an operator station (OS), and to store and show them there. The fast archiving with AR_SEND makes the archiving of process data faster than a 500 ms cycle possible.

Task
In some processes, there is a requirement for data to be archived in rapid cycles.
Since the minimum cycle time of standard archiving in WinCC Tag Logging is 500 ms, an alternative solution is needed.

Solution
To archive a large number of process values in rapid cycles while keeping the load on the system bus as low as possible, the process values are cached in the AS and sent in bundles to the OS with the S7-400 / WinAC RTX system function block AR_SEND / SFB 37.

The ARSCAN_E and AR_MAN_E function blocks were developed based on the AR_SEND block in order to store measured values in the most efficient manner possible and to transfer them to the OS in bundles.

  • The block ARSCAN_E is used for detecting and storing a single process value of the data type REAL or DWORD.
    An ARSCAN_E block is used for each process value.
    There are two ways of detecting the process values:

    • Cyclical acquisition of process data is used to archive process values in an equidistant manner (at fixed intervals of time).

    • Event-driven acquisition of process data is used if a process value is to be archived as soon as its value changes.

  • The block AR_MAN_E includes a FIFO memory for process values and manages the bundled sending of the data to WinCC with the system function block AR_SEND.
    It is possible to connect multiple ARSCAN_E blocks to an AR_MAN_E block (one ARSCAN_E per process value).

The following figure shows a schematic representation of the two blocks used for the fast archiving of process data.

This solution can be used for:

  • Fast archiving of process data with the data types DWORD and REAL (<500ms)

  • Intermediate storage of process data in AS

  • Flexible archiving time for process values (when they change, equidistant, manual)

The use of the function blocks has the following advantages:

  • Easy interconnection of process variables in the CFC editor

  • Simple parameter assignment of the system function block AR_SEND

  • Providing the necessary header information for the AR_SEND block

  • Precise time stamp on process data from the AS

  • Variable trigger options for sending the data to WinCC

  • Automatic frame repetition in case of error

Contents of the Application Example
This Application Example describes the functioning of the fast process value archiving with the function blocks ARSCAN_E und AR_MAN_E. It explains how the blocks work, how they are configured and what boundary conditions must be observed during use.
The application example includes an example project in which the fast archiving of process data was configured for a simulated process value.

The example project provides the following functions:

  • Preconfigured PCS 7 single-user system for use with PLCSIM or real hardware
  • S7 program with simulated process data, two ARSCAN_E blocks with different parameter assignments, one AR_MAN_E block, and blocks for operating the process from the OS or directly from a CFC
  • Preconfigured OS project with two archive tags, a picture for rendering and the export of the archive tags and elements for process control

Validity

  • SIMATIC PCS 7 V9.0 SP1
  • SIMATIC PCS 7 V9.0
  • SIMATIC PCS 7 V8.2
  • SIMATIC PCS 7 V8.1
  • SIMATIC PCS 7 V8.0

The SCL sources can also be used with SIMATIC PCS 7 V7.1.

Downloads

 Registrierung notwendig  Documentation - PCS 7 V9.0 SP1 (2,0 MB)
 Registrierung notwendig  Demo project - PCS 7 V9.0 SP1 (269,2 MB)

  Documentation - PCS 7 V9.0 (2,0 MB)
 Registrierung notwendig  Demo project - PCS 7 V9.0 (211,4 MB)

  Documentation - PCS 7 V8.2 (1,7 MB)
 Registrierung notwendig  Demo project - PCS 7 V8.2 (101,4 MB)

  Documentation - PCS 7 V8.1 (5,6 MB)
 Registrierung notwendig  Demo project - PCS 7 V8.1 (137,6 MB)

  Documentation - PCS 7 V8.0 (596,3 KB)
 Registrierung notwendig  Demo project - PCS 7 V8.0 (62,3 MB)

 Registrierung notwendig  SCL sources (43,6 KB)

Last change
Update of the documentation and application example to SIMATIC PCS 7 V9.0 SP1.

Additional Keywords
RawArchive, #RawArchive, Raw data variable, TagLogging Fast, AR_ID

Security information
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