Siemens 6AV6651-7KA01-3AA4 - S7-1200 + KTP400 Basic Starter Kit 6AV6651-7KA01-3AA4 User Manual
Product codes
6AV6651-7KA01-3AA4
PLC concepts made easy
4.2 Operating modes of the CPU
Easy Book
52
Manual, 03/2014, A5E02486774-AF
STARTUP
RUN
A Clears the input (or "I") memory
①
Writes Q memory to the physical outputs
B Initializes the outputs with either the last
value or the substitute value
②
Copies the state of the physical inputs to I
memory
C Executes the startup OBs
③
Executes the program cycle OBs
D Copies the state of the physical inputs to I
memory
④
Performs self-test diagnostics
E Stores any interrupt events into the queue to
be processed in RUN mode
⑤
Processes interrupts and communications
during any part of the scan cycle
F Enables the writing of the output (or "Q")
memory to the physical outputs
You can change the default behavior for a module by removing it from this automatic update
of I/O. You can also immediately read and write digital and analog I/O values to the modules
when an instruction executes. Immediate reads of physical inputs do not update the process
image input area. Immediate writes to physical outputs update both the process image
output area and the physical output point.
4.2
Operating modes of the CPU
The CPU has three modes of operation: STOP mode, STARTUP mode, and RUN mode.
Status LEDs on the front of the CPU indicate the current mode of operation.
● In STOP mode, the CPU is not executing the program, and you can download a project.
● In STOP mode, the CPU is not executing the program, and you can download a project.
The RUN/STOP LED is solid yellow.
● In STARTUP mode, the CPU executes any startup logic (if present). The CPU does not
process interrupt events during the startup mode. The RUN/STOP LED alternates
flashing between green and yellow.
● In RUN mode, the scan cycle executes repeatedly. Interrupt events can occur and the
CPU can process them at any point within the program cycle phase. You can download
some parts of a project in RUN mode. The RUN/STOP LED is solid green.
The CPU supports the warm restart method for entering the RUN mode. Warm restart does
not include a memory reset, but you can command a memory reset from STEP 7. A memory
reset clears all work memory, clears retentive and non-retentive memory areas, copies load
memory to work memory, and sets outputs to the configured "Reaction to CPU STOP". A
memory reset does not clear the diagnostics buffer or the permanently saved IP address. A
warm restart initializes all non-retentive system and user data.