For EtherNet/IP the maximum data size is 505 Byte O->T and 509 Byte T->O of implicit messaging. For explicit messaging, the assembly size is limitited to 1492 Byte per assembly.
Even if the update cycle of the process data is larger because of the RPC transport, the typically cycle time per communication stack can still be achieved. The update cycle and the cycle time are independet from each other.
The update cycle for process data mapped to RPC depends on the amount of data required to update. Following table shows typical values where the amount of data is mapped to both communication directions (input data and output data) and all data is required to be updated in one cycle. The time required can reach 310 ms, see table below.
used module size per direction
average update cycle
Octet string 1434 Byte
Octet string 1024 Byte
Octet string 512 Byte
Octet string 256 Byte
Octet string 128 Byte
Please note: Access to the RPC objects is not allowed in data mapper callback context. Those objects need to be accessed in the main loop context (e.g. appl_loop()).