Siemens SINUMERIK 840D sl Function Manual page 843

Control signals
Some control signals are signal inputs, for example, via the machine control panel, which have
to be taken into account by the HMI. This group of signals includes, for example, display actual
values in MCS or WCS, key disable, etc. These are exchanged with the HMI via a separate
interface data block (DB19).
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 operation via HMI using an FB1
parameter "MMCToIF".
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 alarm buffer.
The associated message texts must be stored on the OP or HMI.
An FC (FC10) 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
alarm buffer.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
P3: Basic PLC program for SINUMERIK 840D sl
13.9 Interface structure
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