Program Creation - HEIDENHAIN iTNC 530 HSCI Technical Manual

9.7 Program Creation

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Attention
HEIDENHAIN would like to point out the following information for the
processing of signals in the PLC:
For all PLC markers, the status 0 (not set) must be used as the safe

status. Only this way can the safety of a machine be ensured if the power
fails.
The following must be kept in mind for non-volatile markers:

Non-volatile markers, bytes, words and double words can also be deleted
(e.g. if the buffer battery is empty). In order to detect this state, we
recommend setting a flag marker in the non-volatile memory. Set this
marker once, at a time when it is ensured that all signals in the PLC are
valid.
This marker should be used as a reference in the PLC program. As long
as this marker is set, the non-volatile markers have not been deleted (e.g.
by an empty buffer battery or an error in the PLC). If this flag marker is
deleted, all non-volatile markers are invalid. An appropriate safety
reaction with an error message must occur if this happens.
In order to attain an optimum level of safety for your machine and the
operator, HEIDENHAIN recommends the combined use of these safety
measures.
In connection with this, a possibility for outputting the cause of the last PLC
run-time error was introduced. PLC word W1002 can be used to determine
the last PLC run-time error that led to the stop of PLC program execution.
If a PLC run-time error occurs, the generated error code is saved in W1002 and
simultaneously in the non-volatile memory of the control. When a new PLC
run-time error occurs, W1002 and the value in the non-volatile memory are
overwritten.
If the control is restarted or a PLC program start is triggered in some other
manner (by Compile, Restart PLC or acknowledgment of PLC run-time errors),
the value in W1002 regenerates itself via the information in the non-volatile
memory. Once the value has been entered in W1002 again, this information
is deleted from the non-volatile memory. This way the last PLC run-time error
is always available in W1002, even after the PLC is restarted. In addition, the
error code can already be seen in the PLC table as soon as the Power
interrupted status after the control has been restarted.
HEIDENHAIN Technical Manual iTNC 530 HSCI