Siemens AG, 2003. All rights reserved
SINUMERIK 840Di Manual (HBI) – 06.03 Edition
The process output image (POI) will be deleted
Process and diagnostics alarms will be canceled
The system status list will be updated
Parameterization objects of modules (from SD100 onwards) will be evalu-
ated or defaults parameters will be output to all modules in single-processor
OB100 (cold restart) is executed
The process input image (PII) is read in
The command output disable (COD) is canceled.
In cyclic operation, communication or exchange of data and signals is carried
out between the PLC and the components NC, HMI (e.g. HMI Advanced) and
MCP (machine control panel).
The execution of the PLC program is carried out such that – with regard to time
– the basic PLC user program is executed prior to the PLC user program.
Communication of the PLC with the NC is carried out using the NC/PLC inter-
face. The interface is divided into the following areas:
General NC data.
Data exchange through the NC/PLC interface is carried out in the basic PLC
program at the beginning of OB 1. This ensures that the data for the PLC re-
main constant over the entire PLC cycle.
The current G functions of the NC channels are transferred to the PLC (pro-
vided function is activated) on the process alarm level (OB 40).
A cyclic, mutual sign-of-life monitoring function is activated between PLC and
NCK once ramp-up and the first OB1 cycle have been completed.
In case of failure of the PLC or in case of STOP of the PLC program execution,
the following alarm is displayed:
Alarm: "2000 sign-of-life monitoring for PLC".
8 PLC Start-Up
8.4 Testing the PLC program