Processing on Cold Start for Premium/Quantum PLCs

Cause of a Cold Start

The following table describes the different possible causes of a cold start.

Causes	Startup characteristics
Loading of an application	Cold start forced in STOP
RESET button pressed on processor (Premium)	Cold start forced in STOP or RUN mode as defined in the configuration
RESET button pressed on the processor after a processor or system error (Premium).	Cold start forced in STOP
Movement of handle or insertion/removal of a PCMCIA memory card	Cold start forced in STOP or RUN mode as defined in the configuration
Initialization from Control Expert Forcing the system bit %S0	Start in STOP or in RUN (retaining the operating mode in progress at downtime), without initialization of discrete input/output and application-specific modules
Power restored after power supply outage with loss of context	Cold start forced in STOP or RUN mode as defined in the configuration

CAUTION

LOSS OF DATA ON APPLICATION TRANSFER

Loading or transferring an application to the PLC typically involves initialization of unlocated variables.

To save located variables with Premium and Quantum PLCs:

Save and restore %M and %MW by clicking PLC > Transfer Data.

For Premium PLCs:

Avoid the initialization of %MW by un-checking Initialize %MWi on cold start in the configuration screen of the CPU.

For Quantum PLCs:

Avoid the initialization of %MW by un-checking Initialize %MWi in the configuration screen of the CPU.

It is necessary to assign a topological address to the data if the process requires keeping the current values of the data when transferring the application.

Failure to follow these instructions can result in injury or equipment damage.

Illustration

Operation

The table below describes the program execution restart phases on cold restart.

Phase	Description
1	The startup is performed in RUN or in STOP depending on the status of the `Automatic start in RUN` parameter defined in the configuration or, if this is in use, depending on the state of the RUN/STOP input. Program execution is resumed at the start of the cycle.
2	The system carries out the following: the initialization of data (bits, I/O image, words etc.) with the initial values defined in the data editor (value set to 0, if no other initial value has been defined). For %MW words, the values can be retained on cold restart if the Reset of %MW on cold restart option is unchecked in the Configuration screen of the processor. NOTE: %MWi is not retained if a new program is loaded. the initialization of elementary function blocks on the basis of initial data the initialization of data declared in the DFBs: either to 0 or to the initial value declared in the DFB type the initialization of system bits and words the deactivation of tasks, other than the master task, until the end of the first master task cycle the positioning of charts to initial steps the cancellation of any forcing the initialization of message and event queues the sending of configuration parameters to all discrete input/output modules and application-specific modules
3	For this first restart cycle the system does the following: relaunches the master task with the %S0 (cold restart) and %S13 (first cycle in RUN) bits set to 1, and the %SW10 word (detection of a cold restart during the first task cycle) is set to 0 resets the %S0 and %S13 bits to 0, and sets each bit of the word %SW10 to 1 at the end of this first cycle of the master task activates the fast task and event processing at the end of the first cycle of the master task

Phase

Description

The startup is performed in RUN or in STOP depending on the status of the Automatic start in RUN parameter defined in the configuration or, if this is in use, depending on the state of the RUN/STOP input.

Program execution is resumed at the start of the cycle.

The system carries out the following:

the initialization of data (bits, I/O image, words etc.) with the initial values defined in the data editor (value set to 0, if no other initial value has been defined).

For %MW words, the values can be retained on cold restart if the Reset of %MW on cold restart option is unchecked in the Configuration screen of the processor.

NOTE: %MWi is not retained if a new program is loaded.
the initialization of elementary function blocks on the basis of initial data
the initialization of data declared in the DFBs: either to 0 or to the initial value declared in the DFB type
the initialization of system bits and words
the deactivation of tasks, other than the master task, until the end of the first master task cycle
the positioning of charts to initial steps
the cancellation of any forcing
the initialization of message and event queues
the sending of configuration parameters to all discrete input/output modules and application-specific modules

For this first restart cycle the system does the following:

relaunches the master task with the %S0 (cold restart) and %S13 (first cycle in RUN) bits set to 1, and the %SW10 word (detection of a cold restart during the first task cycle) is set to 0
resets the %S0 and %S13 bits to 0, and sets each bit of the word %SW10 to 1 at the end of this first cycle of the master task
activates the fast task and event processing at the end of the first cycle of the master task

Processing a Cold Start by Program

It is advisable to test the bit %SW10.0 to detect a cold start and start processing specific to this cold start.

NOTE: It is possible to test the bit %S0, if the parameter

Automatic
start in RUN

has been selected. If this is not the case, the PLC starts in STOP, the bit %S0 then switches to 1 on the first cycle after restart but is not visible to the program because it is not executed.

Output Changes, for Premium and Atrium

As soon as a power outage is detected, the outputs are set in the fallback position:

either they are assigned the fallback value, or
the current value is maintained

depending on the choice made in the configuration.

After power restore, the outputs remain at zero until they are updated by the task.

Output Changes, for Quantum

As soon as a power outage is detected,

the local outputs are set to zero
the outputs of the remote or distributed extension racks are set in the fallback position

After power is restored, the outputs remain at zero until they are updated by the task.

NOTE: The behavior of forced outputs was changed between Modsoft/NxT/Concept and Control Expert.

With Modsoft/NxT/Concept, you cannot force outputs if the Quantum processor memory protection switch is set to "On".

With Control Expert, you can force outputs if the Quantum processor memory protection switch is set to "On".

With Modsoft/NxT/Concept, forced outputs retain their status after a cold start.

With Control Expert, forced outputs lose their status after a cold start.

CAUTION

UNEXPECTED APPLICATION BEHAVIOR - FORCED VARIABLES

Check your forced variables and memory protection switch when shifting between Modsoft/NxT/Concept and Control Expert.

Failure to follow these instructions can result in injury or equipment damage.

For Quantum 140 CPU 31••/41••/51••

These processors have a Flash EPROM memory of 1,435 KB which can be used to save the program and the initial values of variables.

When power is restored, you can choose the desired operating mode using the PLC MEM switch on the processor front panel. For detailed information on how this switch works, you can consult the Quantum manual.

off position: The application contained in this zone is automatically transferred to internal RAM when the PLC processor is powered up: cold restart of the application.

on position: The application contained in this zone is not transferred to internal RAM: warm restart of the application.