Diagnostic Buffer On Plc - Siemens SINUMERIK 828D Function Manual

P3: Basic PLC Program for SINUMERIK 840D sl
13.6 Coupling of the PLC CPUs
The evaluation and enabling of the G functions transferred from the NCK are also alarm­driven, 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 the
chapter "Start-up of PLC programs".
Interface HMI/PLC
HMI/PLC data exchange takes place via the software C bus or via the Ethernet, internal CP, control-internal C
bus link. The CP transfers the data intact from one bus segment to another. The HMI is always the active partner
(client) and the PLC is always the passive partner (server). Data transmitted or requested by the HMI are 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 are identical to I/O signals.
Interface MCP / PLC, interface HHU / PLC (Ethernet link)
MCP/PLC and HHU (HT2) /PLC data exchange takes place via the integrated CP's Ethernet bus. 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 define
the operand areas (e.g. I/O) and the start addresses via the parameters of the basic programs (FB 1, DB 7).
Interface MCP/PLC (PROFIBUS link)
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 MCP/PLC, interface HHU/PLC (MPI link)
is no longer supported
13.6.4

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
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0