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3.2.3
Command repetition
Operating principle
After a new start (or init_run) of the ASM, the FC 45 transmits the command (or command
chain) once to the ASM. Command transmission is automatic with the first command_start.
This command (or the last command or the command chain) always remains intermediately
stored in the ASM. If command repetition is started now, the intermediately stored command
on the ASM is executed again, and the result(s) transferred to the FC 45.
Advantages of command repetition
• Data transmission on the (PROFI) BUS is minimized. This is particularly noticeable with
• The ASM processes each MDS independently of the FC 45. In concrete terms, this
• Total data throughput is increased considerably particularly with controllers which have
• Use of command repetition to read fixed-code MDSs also has its advantages (see
FC 45
Function manual, Release 03/2006 , J31069-D0167-U001-A2-7618
extensive bus configurations and slow (bus) transmission speeds.
means each MDS is processed even in applications with a very fast sequence of MDSs.
This takes place no matter what the (PROFI) BUS speed.
few system resources for non-cyclic telegrams.
Section "Processing of data memories").
Parameterizing
3.2 MOBY commands
3-19
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