Other Features To Make Programming Easy; System Memory And Clock Memory Provide Standard Functionality - Siemens SIMATIC S7-1200 Manual

Programming concepts made easy

5.4 Other features to make programming easy

MC_MoveAbsolute starts
motion to an absolute position.
The job ends when the target
position is reached.
5.4 Other features to make programming easy
5.4.1

System memory and clock memory provide standard functionality

You use the CPU properties to enable bytes for "system memory" and "clock memory". Your
program logic can reference the individual bits of these functions.
● You can assign one byte in M memory for system memory. The byte of system memory
● You can assign one byte in M memory for clock memory. Each bit of the byte configured
The CPU initializes these bytes on the transition from STOP mode to STARTUP mode, and
the bits of the clock memory change synchronously to the CPU clock throughout STARTUP
and RUN modes.
64
provides the following four bits that can be referenced by your user program:
– "Always off" bit is always set to 0.
– "Always on" bit is always set to 1.
– "Diagnostic graph changed" is set to 1 for one scan after the CPU logs a diagnostic
event.
The CPU does not set the "Diagnostic graph changed" bit until the end of the first
execution of the of the program cycle OBs. Your user program cannot detect if there
has been a diagnostic change either during the execution of the startup OBs or the
first execution of the program cycle OBs.
– "First scan" bit is set to1 for the duration of the first scan after the startup OB finishes.
(After the execution of the first scan, the "first scan" bit is set to 0.)
as clock memory generates a square wave pulse. The byte of clock memory provides 8
different frequencies, from 0.5 Hz (slow) to 10 Hz (fast). You can use these bits as control
bits, especially when combined with edge instructions, to trigger actions in the user
program on a cyclic basis.
MC_MoveRelative starts a
positioning motion relative
to the start position.
MC_MoveVelocity causes
the axis to travel with the
specified speed.
Easy Book
Manual, 11/2009, A5E02486774-01