OWEN Communication Library

[Zulfiqor]

Hi Evgeniy .
I am Using Owen Communication library 3.5.11.3 with SPK110M01.
When Using Function block MB_SerialRequest (FB) with RS-485 port, I do not understand tTimeOut timer functionality. Because When Setting tTimeout := T#100ms, function waits 100ms and gives TimeOutError when reading bigger amount of data blocks that need more than 100ms for completing request task(for example 64 bytes, RTU,9600bps) , I think function block must return TimeOutError : If no response returned in 100ms or Function can calculate approximately time to complete tasks by using relativity by uiDataCount with Baudrate that shown on related hCom port. Thanks.

[Евгений Кислов]

Hi, Zulfiqor.


I think function block must return TimeOutError : If no response returned in 100ms or Function can calculate approximately time to complete tasks by using relativity by uiDataCount with Baudrate that shown on related hCom port. Thanks.

Modbus specifications says:

The master is configured by the user to wait for a predetermined timeout interval ( Response time-out) before aborting the transaction.
This interval is set to be long enough for any slave to respond normally ( unicast request).

https://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf (chapter 2.6)

Therefore, we do not validate the user-specified timeout in any way.
This seems pointless, because the response time depends not only from baudrate / data count, but also from the characteristics of a particular slave, which cannot be taken into account in the calculations.

For your slave device, you can by yourself write a timeout validation function and connect its output to the tTimeout input of our MB_SerialRequest block.

[Zulfiqor]

Hi, Evgeniy.
Thanks for reply.
I learned modbus specification, and You are right.
I must change TimeOut parameter for every request individually.
Thanks.