Siemens SINUMERIK 840D sl Function Manual page 34

A4: Digital and analog NCK I/Os
1.2 NCK I/O via PLC
Isochronous processing
The I/O modules of the external NCK I/Os on the SINUMERIK 840D can be operated in one
of the following two modes:
● Asynchronous
● Synchronous
The processing mode is selected for individual modules by means of general machine data:
MD10384 $MN_HW_CLOCKED_MODULE_MASK[tb]
[tb] = Index for terminal block (0 to 1)
In synchronous processing mode, one of the following clock rates can be selected
(MD10380 $MN_HW_UPDATE_RATE_FASTIO[tb]):
● Synchronous inputs/outputs in position-control cycle (default setting)
● Synchronous inputs/outputs in interpolation cycle
It is possible to define a lead time in microseconds for the clocked NCK I/Os in general
machine data:
MD10382 $MN_HW_LEAD_TIME_FASTIO[tb].
This makes it possible to consider the conversion time of the analog-to-digital converter, for
example, so that the digitized input value is available at the cycle time.
The defined clock rate or rate time applies to all isochronous I/O modules of the terminal
block addressed with [tb].
Monitoring
The following functional monitors are provided for external I/Os on the SINUMERIK 840D:
● During booting:
● During cyclic operation:
In the event of a fault, NC-Ready is canceled and an alarm is output.
Response to faults
In case of malfunction the digital and analog NCK outputs
are switched to "safe" status (0 V at output), in the event of faults (e.g., NC-Ready = 0) in the
NCU or power failures.
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The input and output values are made available in cycles set by the terminal block, which
are asynchronous with the internal NC processing cycles.
The input and output values are made available in synchronism with a settable internal
NC processing cycle.
– Check whether the arrangement of components of the I/O modules in the terminal
blocks matches the MD assignments.
– Sign-of-life monitoring in interpolation cycles
– Module monitoring in interpolation cycles
– Temperature monitoring
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions