Modicon M580 Plc Page 3-15 Communication

3/15 Modicon M580 automation platform Ethernet Modbus/TCP network Performance Application response time Modbus messaging service response time Exchanges between the PLC CPU and the Ethernet module are synchronous with the PLC scan cycle time (CT), just like the I/O exchanges. When an event occurs (such as an input being set to 1 for example), a message can be transmitted only after this input has been taken into account (start of the next cycle) and the PLC (Modicon M340, Modicon Premium, or Modicon Quantum) program has been executed, i.e. on average approximately 1.5 cycles after the event occurred. The transaction time TT includes the delay between the transmission of a message from a client station 1, its reception by the server station 2, processing the request, sending back the response, and it being taken into account by station 1 (updating an output for example). As the block diagram above shows: b The transaction time TT will be between: 2 x CT1 + 2 x NAT < TT < 4 x CT1 + CT2 + 2 x NAT b The average duration TT av is equivalent to: TT av = 3 x CT1 + 0.5 x CT2 + 2 x NAT Performance (continued) Modbus messaging service response time Station 1 Event CT1 NAT CT2 CT2 Station 2 Report TT CT1 CT1 CT1 Action Processors: page 1/20 I/O architectures: page 2/2 Ruggedized Modicon M580 modules: page 4/2 2 1 3 4 5 6 7 8 9 10 2 1 3 4 5 6 7 8 9 10

Previous Page
Next Page