Definitions: PLC System Start-up

Cold start

  • A cold start is performed by switching power OFF/ON if no battery is connected.
  • All RAM memory modules are checked and erased (see Command ‘Reset cold’: Command ‘Reset cold’
  • If no user program is stored in the Flash EPROM, the default values (as set on delivery) are applied to the interfaces.
  • If there is a user program stored in the Flash EPROM, it is loaded into RAM.
  • The default operating modes set by the PLC configuration are applied.

Warm start

  • A warm start is performed by switching power OFF/ON with a battery connected.
  • All RAM memory modules are checked and erased except of the buffered operand areas and the RETAIN variables (see Command ‘Reset warm’: Command ‘Reset warm’
  • If there is a user program stored in the Flash EPROM, it is loaded into RAM.
  • The default operating modes set by the PLC configuration are applied.

RUN -> STOP

  • RUN -> STOP means pressing the RUN function key on the PLC while the PLC is in run mode (PLC display “run”).
  • If a user program is loaded into RAM, execution is stopped.
  • All outputs are set to FALSE or 0.
  • Variables keep their current values, i.e., they are not initialized.
  • The PLC display changes from “run” to “StoP”.

START -> STOP

  • START -> STOP means stopping the execution of the user program in the PLC’s RAM using the menu item “Online/Stop” in the programming system.
  • All outputs are set to FALSE or 0.
  • Variables keep their current values, i.e., they are not initialized.
  • The PLC display changes from “run” to “StoP”.

Reset

  • Performs a START -> STOP process.
  • Preparation for program restart, i.e., the variables (VAR) (exception: RETAIN variables) are set to their initialization values.
  • Reset is performed using the menu item “Online/Reset” in the programming system or pressing the function key RUN for ≥ 5 s in STOP mode.

Reset (cold)

  • Performs a START -> STOP process.
  • Preparation for program restart, i.e., the variables (VAR) (also RETAIN variables) are set to their initialization values.
  • Reset (cold) is performed using the menu item “Online/Reset (cold)” in the programming system.

Reset (original)

  • Resets the controller to its original state (deletion of Flash, SRAM (%M, area, %R area, RETAIN, RETAIN PERSISTENT), Communication Module configurations and user program!).
  • Reset (original) is performed using the menu item “Online/Reset (original)” in the programming system.

STOP -> RUN

  • STOP -> RUN means short pressing the RUN function key on the PLC while the PLC is in STOP mode (PLC display “StoP”).
  • If a user program is loaded into RAM, execution is continued, i.e., variables will not be set to their initialization values.
  • The PLC display changes from “StoP” to “run”.

STOP -> START

  • STOP -> START means continuing the execution of the user program in the PLC’s RAM using the menu item “Online/Start” in the programming system.
  • If a user program is loaded into RAM, execution is continued, i.e., variables will not be set to their initialization values.
  • The PLC display changes from “StoP” to “run”.

Download

  • Download means loading the complete user program into the PLC’s RAM. This process is started by selecting the menu item “Online/Download” in the programming system or after confirming a corresponding system message when switching to online mode (menu item “Online/Login”).
  • Execution of the user program is stopped.
  • In order to store the user program to the Flash memory, the menu item “Online/Create boot project” must be called after downloading the program.
  • Variables are set to their initialization values according to the initialization table.
  • RETAIN variables can have wrong values as they can be allocated to other memory addresses in the new project!
  • A download is forced by the following:
    • changed PLC configuration
    • changed task configuration
    • changed library management
    • changed compile-specific settings (segment sizes)
    • execution of the commands “Project/Clean all” and “Project/Rebuild All”.

Online Change

  • After a project has changed, only these changes are compiled when pressing the key <F11> or calling the menu item “Project/Build”. The changed program parts are marked with a blue arrow in the block list.
  • The term Online Change means loading the changes made in the user program into the PLC’s RAM using the programming system (after confirming a corresponding system message when switching to online mode, menu item “Online/Login”).
  • Execution of the user program is not stopped. After downloading the program changes, the program is re-organized. During re-organization, no further online change command is allowed. The storage of the user program to the Flash memory using the command “Online/Create boot project” cannot be initiated until re-organization is completed.
  • Online Change is not possible after:
    • changes in the PLC configuration
    • changes in the task configuration
    • changes in the library management
    • changed compile-specific settings (segment sizes)
    • performing the commands “Project/Clean all” and “Project/Rebuild All”.

Data buffering

  • Data buffering, i.e., maintaining data after power ON/OFF, is only possible, if a battery is connected. The following data can be buffered completely or in parts:
    • Data in the addressable flag area (%M area)
    • RETAIN variable
    • PERSISTENT variable (number is limited, no structured variables)
    • PERSISTENT area (%R area)
  • In order to buffer particular data, the data must be excluded from the initialization process (see Initialization of Variables: Data Backup and Initialization