7
03/2006
7.1 PLC start-up
7-161
© Siemens AG 2006 All Rights Reserved
SINUMERIK 840D/810D Start-Up Guide (IADC) – 03/2006 Edition
Note
The STEP7 project manager (S7 TOP) does not display the SDB as standard.
To display the SDB, select “All blocks with SDBs” from the “View” –> “Set filters”
menu.
The “Diagnostics” menu includes the PLC status option for controlling and moni-
toring PLC inputs, outputs, flags, etc.
The PLC always powers up in RESTART mode, i.e. the PLC operating system
runs through OB100 after initializing and then starts cyclical operation at the
start of OB1. No re-entry takes place at the interruption point (e.g. after power
failure).
For the flags, timers and counters there are both retentive and non-retentive
areas. Both area types are contiguous, but are separated by a parameterizable
limit, the area with the higher-order address being designated as the non-reten-
tive area. Data blocks are always retentive.
If the retentive area is not buffered (back-up battery empty), then start-up is
blocked. The following operations are performed during a restart:
S Delete IStack, BStack and non-retentive flags, timers and counters
S Delete process output image (POI)
S Reject process and diagnostic alarms
S Update system status list
S Evaluate parameterization objects of modules (from SD100 onwards) or
output default parameters to all modules in single-processor mode
S Process restart OB (OB100)
S Read in process input image (PII)
S Cancel command output disable (BASP)
The basic program before the PLC user program is processed. In cyclic opera-
tion, the NC/PLC interface is fully processed. At the process alarm level, the
current G functions are transferred to the PLC, if this function is active.
A cyclic monitoring function is activated between the PLC and NCK once
power-up and the first OB1 cycle have been completed. When the PLC fails,
alarm “2000 sign of life monitoring PLC” is displayed.
Reference material: /FB1/ P3, Function guide,
PLC basic program powerline
/S7H/ SIMATIC S7-300
PLC status
Starting characteri-
stics of the PLC
RESTART mode
Cyclical operation
Sign-of-life
monitoring
7 PLC Descri
tion
To Next Page
Loading...
