Today is:   Feb 23, 2019

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Institute Mihailo Pupin
Institute Mihailo Pupin is the leading Serbian R&D institution in the field of Information & Communication Techologies.

Automation & Control Systems Ltd
The Automation & Control Systems Ltd is the core division of the Institute Mihailo Pupin, and the owner of the projects: ATLAS Systems and ATLAS-MAX.

The long list of the Institute's references and customers is the best proof of its high professional and techological achievments.

The other related IMP project: VIEW4 Software Package for control of complex processes

Ladder Diagram Upload


Once a ladder diagram was created, there are few more steps before its real-life implementation.  A ladder diagram must be tested off-line, compiled into ATLAS executable code, debugged on-line, and finally (if everything went smoothly) uploaded into the ATLAS system firmware.  Generally, ATLAS data uploads could be done in three ways, or more precisely, in three upload modes:

  • In off-line mode, when ATLAS system is out of production;
  • In service mode, when ATLAS system is temporarily out of operation;
  • In on-line mode, when ATLAS system is in full operation.

Each of the listed modes could be realized via ATLAS-PT Programming Terminal.  However, first two modes allow even a manual replacement of the hot-pluggable ATLAS memory chip, what presents a trivial upload procedure that is recommended whenever is applicable.  Conventionally, the compiled and executable ladder data are kept as files and ladder code upload means uploading of the created files, which are than linked with the internal PLC execution program for future system start-ups.  Technically, this is a user-friendly straight-forward procedure.  By choosing the Ledcopy option in the MAIN MENU, the Upload Window is invoked.  The remaining procedure is very intuitive.


New ladder code always carries certain risk in the real-life implementation.  Whenever a ladder replacement is uploaded, it is important to be ready to recover the old ladder if needed.  This is also an elaborated menu-driven upload procedure, but still it is taking some time during whom the on-line ladder execution is suspended.

In the case of a redundant master/slave ATLAS PLC system, the possible upload scenarios are:

  • -If a new ladder is uploaded into the master PLC unit, the previous ladder is suspended and the new one started.  If something went wrong, an automatic failover to the slave PLC unit will activate back the old ladder (the slave PLC unit does not know about the new ladder).
  • -If a new ladder is uploaded into the slave PLC unit, to check its functionality the master/slave switchover is forced, and a new ladder started on a new master PLC unit.  If something went wrong with new ladder, an automatic failover to the previous master PLC unit (still with the old ladder) occurs and “the good old ladder” is back in business.

In both cases, if a new ladder fails, the previous good ladder version should be reinstalled on the affected PLC unit.  Luckily, at that time an affected PLC unit is always the slave one, and the “recovery procedure” does not conflict with a production.