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) 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 are used to transmit and receive data between network devices and PLC 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.
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 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%.
