Siemens SINUMERIK 840Di Function Manual page 1224

Detailed Description
2.6 Interface structure
2.6.2 Interface PLC/HMI
General
The following groups of functions are required for the PLC/HMI interface:
• Control signals
• Machine operation
• PLC messages
• PLC status display
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 via 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 events, which lead to a system stop, are also entered with a time stamp in a
2-30
diagnostics status list. Communication events and I/O module diagnostics data (for
modules with diagnostic functions) are also entered.
diagnostic buffer (circular buffer) in the chronological order of their occurrence.
PLC Basic Program Solution Line (P3 sl)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0