Estimating The Modbus Master Cpu Load - WAGO 750-8215 Manual

WAGO-I/O-SYSTEM 750
750-8215 PFC200; G2; 4ETH CAN USB
9.3

Estimating the Modbus Master CPU Load

Due to the real-time characteristics of the Linux kernel used, many data points
can generate many context changes.
For a one-off update (transmitting and receiving of a function code), a CPU time
of approx. 800 µs can be assumed.
The CPU load (cpu_load) in percent can be estimated from the cycle time (t_z)
for a query with the following rule of thumb:
A cycle time of 100 ms thus results in a CPU load of 0.8%.
A maximum load of approx. 20% can be generated per connection, as this is
limited by the network protocol. To minimize the CPU load:
- The cycle time must be as high as possible.
- As many data points as possible must be combined in a query.
- The minimum query interval can be increased (default value: 0 ms).
cpu_load = 800 µs / t_z * 100
Version 1.2.0, valid from FW Version 03.02.02(14)
Modbus – e!RUNTIME 237
Manual