Diagnostic Buffer On Plc - Siemens SINUMERIK 840D sl Function Manual

(e.g. M08 for cooling medium on), the transfer of these "fast" auxiliary functions is directly
acknowledged in OB40, so that decoding is only insignificantly influenced by the transfer to
the PLC.
The evaluation and enabling of the G functions transferred from the NCK are also alarm-driven,
however they are transferred directly to the user interface. Where a G function is evaluated at
several points in the PLC program, differences in the information of the G function within one
PLC cycle may arise.
In the case of NC actions triggered and assigned with parameters by the PLC (e.g. traverse
concurrent axes), triggering and parameter assignment is performed using FCs and FBs, not
interface data blocks. The FCs and FBs belonging to the actions are supplied together with
the basic program. The FCs and FBs required must be loaded by the user and called in the
PLC program of the machine manufacturer (machine program). For an overview of FC, FB
and data blocks, sorted according to basic and extended functions, please refer to Section
"Start-up of PLC programs".
Interface: HMI/PLC
HMI/PLC data exchange is performed via the integrated CP, whereby the HMI is always the
active partner (client) and the PLC is always the passive partner (server). Data transferred or
requested by the HMI is read from and written to the HMI/PLC interface area by the PLC
operating system (timing: Cycle control point). From the viewpoint of the PLC application, the
data is identical to I/O signals.
Interface: MCP/PLC or HHU/PLC (connection: Ethernet)
MCP/PLC and HHU (HT 2) / PLC data is exchanged via the integrated CP. The CP transfers
the MCP/HHU signals to and fetches them from the PLC's internal DPR (Dual-Port RAM). On
the PLC side, the basic program handles communication with the user interface. The basic-
program parameters (FB1, DB7) define the operand areas (e.g. I/O areas) and the start
addresses.
Interface: MCP/PLC (connection: PROFIBUS)
MCP/PLC data exchange takes place via the PLC's PROFIBUS. The MCP's I/O addresses
are to be set in the PLC's process image area and via HW configuration in STEP 7. The
MCP*In, MCP*Out pointer variables must be set to the same addresses. The selected DP
slave number must be entered in MCP*BusAdr.
Interface: HHU/PLC (connection: MPI)
The HHU/PLC data exchange is performed via the MPI interface on the PLC. The
"Communication with global data (GD)" service is used for this purpose (see also STEP 7 User
Manual). The PLC operating system handles the transfer of signals from and to the user
interface. The STEP 7 "Communication configuration" configuring tool is used to define both
GD parameters as well as operand areas (e.g. I/O areas) and their start addresses.
13.8.4

Diagnostic buffer on PLC

The diagnostic buffer of the PLC (readable using STEP 7) will enter diagnostic information on
the PLC operating system.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
P3: Basic PLC program for SINUMERIK 840D sl
13.8 Coupling of the PLC CPU
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