Plc Alarms - Siemens SINUMERIK 802C base line Technical Manual

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4.3.3

PLC alarms

Alarm response and cancel criterion
Possible alarm responses are:
4-12
The Run mode activates the cyclic mode.
In the Stop mode, the following actions are initiated:
All hardware outputs are disabled.
z
The NC Ready relay is inactive.
z
No cyclic operation (active user program is not executed)
z
Process image is no longer updated ("frozen")
z
Emergency Stop active
z
The user can also use the PLC 802 Programming Tool to start the Stop or Run
modes.
A corrected or new project can only be loaded into the control system in the
Stop mode. The user program comes only into effect with next power-up or
when the Run mode is active.
The control system displays a maximum of 8 PLC alarms (system alarms or
user alarms).
The PLC manages the alarm information per PLC cycle. It stores or deletes the
alarms in the alarm list according to their occurrence. The first alarm in the list
is generally the alarm last occurred.
If more than 8 alarms occur, the first seven alarms occured are displayed, and
the last one with the highest cancel priority is displayed.
Furthermore, the PLC manages the alarm responses. The alarm responses
are always active, irrespective of the number of active alarms. Depending on
the type of the alarm response, the PLC triggers an appropriate response.
Each alarm requires a cancel criterion to be defined. The PLC uses the SELF-
CLEARING criterion as default criterion.
Cancel criteria are:
POWERONCLEAR: The alarm is canceled by switching off/switching on
z
the control system.
CANCELCLEAR: The alarm is canceled by pressing the Cancel key or
z
the Reset key (analogously to CNC alarms).
SELF-CLEARING: The alarm is cleared because the cause resulting in
z
the alarm has been eliminated or does not exist any longer.
Desired alarm responses are defined for each alarm in the PLC. By default, the
PLC uses the SHOWALARM response (bit0 - bit5 = 0).
PLC Stop : The user program is no longer executed, the NC Ready relay
z
drops out, and the hardware outputs are disabled ( OUTDS ).
EMERGENCY STOP: The PLC provides the EMERGENCY STOP signal
z
to the CNC in the user interface after the user program has been
executed.
SINUMERIK 802C base line
Start-Up