Parameterizing
3.2 MOBY commands
FC 45
Function manual, Release 03/2006 , J31069-D0167-U001-A2-7618
3-19
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
extensive bus configurations and slow (bus) transmission speeds.
•
The ASM processes each MDS independently of the FC 45. In concrete terms, this
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.
•
Total data throughput is increased considerably particularly with controllers which have
few system resources for non-cyclic telegrams.
•
Use of command repetition to read fixed-code MDSs also has its advantages (see
Section "Processing of data memories").