Time-Interrupt Processing (Ob35); Process-Interrupt Processing (Ob 40) - Siemens SINUMERIK 840D sl Function Manual

G group decoders
In the case of G functions sent by the NCK, the related groups are decoded and the current
G number is entered in the corresponding interface byte of the CHANNEL DB, i.e. all active
G functions are entered in the channel DBs. The entered G functions are retained even after
the NC program has terminated or aborted.
Note
During system startup, all G group bytes are initialized with the value "0".
M, S, F distributor
The M, S, F, distributor is used to enter spindle-specific M words M(1...6)=[3,4,5], S words and
F words for axial feeds in the appropriate spindle and axis data blocks. The criterion for
distribution is the extended address which is passed to the PLC for M words, S words and
axial F words.
MCP signal transmission
Depending on the bus connection, the MCP signals are either transmitted directly to the PLC
or indirectly to the parameterized I/O areas via an internal procedure using the basic program.
User messages
The acquisition and processing of the user error and operational messages is performed by
an FC in the basic program.
13.10.3

Time-interrupt processing (OB35)

The user must program OB35 for time-interrupt processing. The default time base setting of
OB 35 is 100 ms. A different time base can be selected using the STEP7 "HW Config" tools.
However, the OB35 time setting must be at least 3 ms in order to avoid a PLC CPU stop. The
stop is caused by reading of the HMI system state list during powerup of the HMI. This reading
process blocks priority class control for approx. 2 ms. The OB35 with a time base set to a
rather lower value is then no longer processed correctly.
13.10.4

Process-interrupt processing (OB 40)

A process interrupt OB40 (interrupt) can, for example, be triggered by appropriately configured
I/Os or by certain NC functions. Due to the different origin of the interrupt, the PLC user program
must first interpret the cause of the interrupt in OB40. The cause of the interrupt is contained
in the local data of OB40.
References:
SIMATIC STEP 7 Description or Online Help of STEP 7
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
P3: Basic PLC program for SINUMERIK 840D sl
13.10 Structure and functions of the basic program
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