S_AutoReset input

This input is used to specify the restart inhibit after the safety-related equipment has been closed (S_Guard = SAFETRUE) and locked (S_GuardLock = SAFETRUE).

When a restart inhibit is active, all safety-related outputs of the function block are in the defined safe state. This ensures that a machine/system cannot be restarted inadvertently. If a restart inhibit has been specified, a reset signal is required to remove the inhibit and enable the machine/system to function.

Data type: SAFEBOOL
Initial value: SAFEFALSE

Connection: Connect this input to a variable or constant.

If Activate = TRUE, the possible values at S_AutoReset lead to the following function block behavior:

Value Description

SAFETRUE No restart inhibit after the safety-related equipment has been closed (S_Guard = SAFETRUE) and locked (S_GuardLock = SAFETRUE).
If no restart inhibit has been specified for the function block, the SAFETRUE status at the S_GuardLock input can cause the S_GuardLocked output to immediately switch to SAFETRUE.1, 2

SAFEFALSE Active restart inhibit after the safety-related equipment has been closed (S_Guard = SAFETRUE) and locked (S_GuardLock = SAFETRUE).
The restart inhibit must be manually removed by means of a reset signal (positive signal edge) at the Reset input.3

Value	Description
SAFETRUE	No restart inhibit after the safety-related equipment has been closed (S_Guard = SAFETRUE) and locked (S_GuardLock = SAFETRUE). If no restart inhibit has been specified for the function block, the SAFETRUE status at the S_GuardLock input can cause the S_GuardLocked output to immediately switch to SAFETRUE.1, 2
SAFEFALSE	Active restart inhibit after the safety-related equipment has been closed (S_Guard = SAFETRUE) and locked (S_GuardLock = SAFETRUE). The restart inhibit must be manually removed by means of a reset signal (positive signal edge) at the Reset input.3

1 If no restart inhibit is specified, observe the following:

WARNUNG

Unintended start-up

Be sure that your risk analysis includes an evaluation for the state change at the S_GuardLocked output after applying SAFETRUE to the S_GuardLock input.

Make certain that appropriate procedures and measures (according to applicable sector standards) have been established to help avoid hazardous situations when applying SAFETRUE to the S_GuardLock input.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

2 If no restart inhibit is specified, observe the following:

WARNUNG

Unintended start-up

Be sure that your risk analysis includes an evaluation for when the safety-related function is no longer requested (S_GuardLocked = SAFETRUE).

Make certain that appropriate procedures and measures have been taken to avoid an unintended restart when applying the SAFETRUE status to the S_AutoReset input.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

WARNUNG

Non-conformance to safety function requirements

Verify that a restart inhibit facility is implemented in your safety-related network if required for your specific safety-related function according to the relevant standards.

3 Removing the restart inhibit by means of a positive signal edge at the Reset input can cause the S_GuardLocked output to switch to SAFETRUE immediately.

WARNUNG

Unintended start-up

Verify the impact of removing the restart inhibit by means of a positive signal edge at the Reset input.

Make certain that appropriate procedures and measures (according to applicable sector standards) have been taken to help avoid hazardous situations when removing the restart inhibit.

Do not enter the zone of operation when removing the start-up inhibit.

Ensure that no other persons can access the zone of operation when removing the start-up inhibit.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

WARNUNG

Unintended start-up

Validate the behavior of the function block and the safety-related network as a whole and thoroughly test the application.