Controller Performance Guidelines

Time to share the data over EtherNet/IP or PROFINET does not increase as more variables are shared unless either the:

EtherNet/IP Requested Packet Interval (RPI "Requested Packet Interval") time is changed.

PROFINET Send clock factor is changed.

PCMM2G processor is overloaded (i.e., no idle time).

Additional controller CPU usage is required when fieldbuses A Fieldbus is an industrial network system for real-time distributed control (e.g. CAN or Profibus). It is a way of connecting instruments in a plant design are used to transmit and receive data between network devices and PLC "Programmable Logic Controller" A Programmable Logic Controller, PLC, or Programmable Controller is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. Used to synchronize the flow of inputs from (physical) sensors and events with the flow of outputs to actuators and events variables.

The impact to the PLC execution time and the CPU load is estimated as:

EtherNet/IP or PROFINET Processing Time = PLC Overhead + (Bytes Shared x Load per Byte)

These models are used to calculate the performance of the EtherNet/IP and PROFINET fieldbuses.

AKD PDMM and PCMM - 800MHz
AKD PDMM and PCMM - 1.2GHz
PCMM2G

Notes

The Load per Byte is dependent on both the:
- EtherNet/IP RPI.
- PROFINET Send clock factor.
The Load per Byte values are measured with both:
- EtherNet/IP: RPI = 10.
- PROFINET: Send clock factor [31,250us] = 32.

AKD PDMM and PCMM - 800MHz

AKD PDMM and PCMM 800MHz 800MHz as an:	PLC Overhead	Load per Byte
EtherNet/IP Adapter (Server)	42 microseconds	0.5258 microsecond/Byte
EtherNet/IP I/O Scanner (Client)	42 microseconds	0.4603 microsecond/Byte

AKD PDMM and PCMM - 1.2GHz

AKD PDMM and PCMM 800MHz 1.2GHz as an:	PLC Overhead	Load per Byte
EtherNet/IP Adapter (Server)	28 microseconds	0.3121 microsecond/Byte
EtherNet/IP I/O Scanner (Client)	25 microseconds	0.269 microsecond/Byte
PROFINET IO Controller	54 microseconds	0.515 microsecond/Byte
PROFINET IO Device	25 microseconds	0.235 microsecond/Byte

PCMM2G

PCMM2G as an:	PLC Overhead	Load per Byte
EtherNet/IP Adapter (Server)	15 microseconds	0.0922 microsecond/Byte
EtherNet/IP I/O Scanner (Client)	10 microseconds	0.0753 microsecond/Byte
PROFINET IO Controller	22 microseconds	0.156 microsecond/Byte
PROFINET IO Device	13 microseconds	0.119 microsecond/Byte

Example: EtherNet/IP Performance

This example uses an PCMM2G as an I/O Scanner with 8x Assemblies with:

3968 Byte PLC variables all with RPI 10ms.

4000 microsecond EtherCAT ***EtherCAT is an open, high-performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times (also called cycle times) with low communication jitter (for synchronization purposes) and low hardware costs Cycle Time.

PLC Time = (3968 x 0.0922) + 15 = 381 microseconds 
CPU Usage % = 381 / 4000 = 0.095 (9.5%)

Results of exchanging data over EtherNet/IP:

Increases the PLC execution time by 381 microseconds.

Reduces the CPU Idle Time by 9.5%.