Communication via Function Blocks 
  6.6 Technical Specifications of the Function Blocks 
Point-to-point connection CP 440 Installation and Parameter Assignment 
Manual, 09/2007, A5E00057742-03 
109 
Minimum Number of CPU Cycles 
The table below describes the minimum number of CPU cycles (FB/FC calls) required to 
process a "minimum request" (32 bytes SEND/RECEIVE for the transported user data set 
per program cycle). This applies only in centralized operation. 
Table 6-10  Minimum Number of CPU Cycles 
  Number of CPU Cycles for Processing ... 
  Completion without error  Completion with error  RESET/RESTART 
RECV_440  ≥ 2  ≥ 2  ≥ 3 
SEND_440  ≥ 2  ≥ 2  ≥ 3 
RES_RECV  ≥ 2  ≥ 2  ≥ 3 
 
Before the CP 440 can process an initiated job after the CPU has changed from STOP to 
RUN mode, the CP-CPU startup mechanism SEND_440 must be completed. Any requests 
initiated in the meantime do not get lost. They are transmitted once the startup coordination 
with the CP 440 is finished. 
Before the CP 440 can receive or submit a frame in the user program after a change in the 
CPU mode from STOP to RUN, the CP-CPU startup mechanism RECV_440 must be 
completed. 
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