Siemens SINUMERIK 840D sl Function Manual page 822

P3: Basic PLC program for SINUMERIK 840D sl
13.1 Brief description
Event-driven signal exchange PLC → NCK
An "event driven signal exchange PLC → NCK" takes place whenever the PLC transfers a
request to the NCK (e.g. traversal of an auxiliary axis). In this case, data transfer is also
acknowledgement-driven. When performed from the user program, this type of signal
exchange is triggered using a function block (FB) or function call (FC).
The associated FBs (Function Blocks) and FCs (Function Calls) are supplied together with the
basic program.
Messages
User messages are acquired and conditioned by the basic program. The message signals are
transferred to the basic program via a specified bit array. where they are evaluated and, if
message events occur, entered in the PLC's interrupt buffer by means of the ALARM S/SQ
functions. If an HMI (e.g. SINUMERIK Operate) is being used, the messages are transferred
to the HMI and displayed.
PLC/HMI data exchange
In this type of data exchange, the HMI takes the initiative, being referred to as the "client" on
the bus system. The HMI polls or writes data. The PLC processes these requests at the cycle
control point via the operating system. The PLC basic program is not involved in these
exchanges.
Note
The function of the machine is largely determined by the PLC program. Every PLC program
in the RAM can be edited with the programming device.
Know-how protection for user blocks
To protect the know-how contained in the the user blocks (OB, FB and FC), they can be
encoded with the SBP tool (SIMATIC block protection) contained in SIMATIC STEP 7. These
blocks can then no longer be opened, debugged and modified without specifying the password
for the encoding.
When encoding, the automation system on whose PLC-CPU the blocks are to be executed,
must be specified: SIMATIC and/or SINUMERIK PLC-CPU.
The handling of the blocks, e.g. loading to the CPU, is not affected by the encoding.
Requirement
SIMATIC STEP 7 as of Version 5.5 SP3
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Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions