Siemens SINUMERIK 828D Function Manual page 869

Machine operation
All operator inputs, which lead to response actions on the machine, are monitored by the PLC. Operator actions
are usually performed on the machine control panel (MCP). However, it is also possible to perform some
operator actions on the HMI e.g. mode selection.
The PLC operating system enters the operating signals sent by the HMI directly into the interface data blocks. As
standard, the basic program routes these operating signals in such a way that, provided equivalent operator
actions are available, these can be performed either on the HMI or on the MCP. If required, the user can switch
off the operation via HMI through a parameter "MMCToIF" of FB1.
PLC messages
The signaling functions are based on the system diagnostic functions integrated in the operating system of the
AS 300. These have the following characteristics:
• The PLC operating system enters all important system states and state transitions in a diagnostics status list.
Communication events and I/O module diagnostics data (for modules with diagnostic functions) are also
entered.
• Diagnostics events, which lead to a system stop, are also entered with a time stamp in a diagnostic buffer
(circular buffer) in the chronological order of their occurrence.
• The events entered in the diagnostic buffer are automatically transmitted to human machine interface systems
(OP or HMI) via the bus systems once these have issued a ready signal (message service). Transfer to the
node ready is a function of the PLC operating system. Receipt and interpretation of the messages are
executed by the HMI software.
• The PLC user program can also use SFCs (System Function Calls) to enter messages in the diagnostic buffer
or ALARM S/ALARM SQ buffer.
• The events are entered in the interrupt buffer.
The associated message texts must be stored on the OP or HMI.
An FC (FC 10) for message acquisition is prepared in conjunction with the basic program. This FC records
events, subdivides them into signal groups and reports them to the HMI via the interrupt buffer.
The message acquisition structure is shown in the figure "Acquisition and signaling of PLC events". The features
include:
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
P3: Basic PLC Program for SINUMERIK 840D sl
13.7 Interface structure
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