Introduction

The M580 safety PAC can enter the start-up sequence in the following circumstances:

  • At initial power-up.

  • In response to a power interruption.

Depending on the type of task, and the context of the power interruption, the M580 safety PAC may perform either a cold start or a warm start when power is restored.

Initial Start-Up

At initial start-up, the M580 safety PAC performs a cold start. All tasks, including both the SAFE task and the non-safe (MAST, FAST, AUX0, AUX1) tasks, enter the STOP state unless Automatic start in RUN is enabled, in which case all tasks enter the RUN state.

Start-Up after a Power Interruption

The M580 safety power supply provides a power reserve that continues to supply all modules on the rack for up to 10 ms in case of a power interruption. When the power reserve is depleted, the M580 safety PAC performs a complete power cycle.

Before powering down the system, the safety CPU stores the following data that defines the operating context at power down:

  • Date and time of the power down (stored in %SW54...%SW58).

  • State of each task.

  • State of event timers.

  • Values of running counters.

  • Signature of the application.

  • Application data (current values of application variables)

  • Application check sum.

After power down, the start-up can be either automatic (if power was restored before completion of the shut-down) or manual (if not).

Next, the M580 safety PAC performs self-tests and checks the validity of the operating context data that was saved at power down, as follows:

  • The application check sum is verified.

  • The SD memory card is read to confirm that is contains a valid application.

  • If the application in the SD memory card is valid, the signatures are checked to confirm they are identical.

  • The saved application signature is verified by comparing it to the stored application signature.

If the operating context is valid, the non-safe tasks perform a warm start. If the operating context is not valid, the non-safe tasks perform a cold start. In either case, the SAFE task performs a cold start.

This start-up sequence after a power interruption is presented, below:

Cold Start

A cold start causes all tasks, including both the SAFE task and the non-safe (MAST, FAST, AUX0, AUX1) tasks, enter the STOP state, unless Automatic start in RUN is enabled, in which case all tasks enter the RUN state.

A cold start performs the following operations:

  • Application data (including internal bits, I/O data, internal words, and so forth) are assigned the initial values defined by the application.

  • Elementary functions are set to their default values.

  • Elementary function blocks and their variables are set to their default values.

  • System bits and words are set to their default values.

  • Initializes all forced variables by applying their default (initialized) values.

A cold start can be executed for data, variables and functions in the process namespace by selecting PLC > Init in Control Expert, or by setting the system bit %S0 (COLDSTART) to 1. The %S0 system bit has no effect on the data and functions belonging to the safe namespace.

NOTE: Following a cold start, the SAFE task cannot start until after the MAST task has started.

Warm Start

A warm start causes each process task – including the (MAST, FAST, AUX0, AUX1) tasks – to re-enter its operating state as of the time of the power interruption. By contrast, a warm start causes the SAFE task to enter the STOP state, unless Automatic start in RUN is selected.

NOTE: If a task was in the HALT state or in breakpoint at the time of power interruption, that task enters the STOP state after the warm start.

A warm start performs the following operations:

  • Restores the last held value to process namespace variables.

  • Initializes safe namespace variables by applying their default (initialized) values.

  • Initializes all forced variables by applying their default (initialized) values.

  • Restores the last held value to application variables.

  • Sets %S1 (WARMSTART) to 1.

  • Connections between the PAC and CPU are reset.

  • I/O modules are re-configured (if necessary) using their stored settings.

  • Events, the FAST task, and the AUX tasks are disabled.

  • The MAST task is re-started from the beginning of the cycle.

  • %S1 is set to 0 at the conclusion of the first execution of the MAST task.

  • Events, the FAST task, and the AUX tasks are enabled.

If a task was in the process of execution at the time of power interruption, after warm start the task resumes execution at the beginning of the task.