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Performance

This section presents the performance and limitations of the Asycube Modbus TCP implementation.

Communication

The Asycube only accepts one Modbus master/client to be connected at a time. However, a TCP/IP connection can be used in parallel with Modbus; this can be useful to use the Asycube Studio to configure the Asycube while a machine PLC controls the Asycube through Modbus.

The Asycube can only handle one read or write request at a time. If two requests are sent simultaneously, the second one will be ignored. It is recommended to alternate between the different read/write requests.

As stated in the Modbus protocol specification, up to 125 registers can be read at once and only up to 123 registers can be written at once. If more registers need to be read (or written), you will have to implement multiple read (or write) requests one after the other.

Timing

The Asycube is able to handle one Modbus read or write request every 4 ms. The timing performance of a Modbus command (e.g. trigger the start of a platform vibration) depends on different factors such as the Modbus master implementation or the Ethernet network state.

Therefore, it is not possible to guarantee neither real-time behavior nor maximal reaction time. The order of magnitude for the delay between a Modbus command and its effect on the Asycube is 10 ms.

The delay between the instant when a register is written and the instant when its updated value is read on Modbus typically lays around 15 ms.