Hi.
I have encoutered a problem in my code:
I am using a cRIO 9012 with FPGA utilize a NI 9871 4-port RS-485 module.
My code is using FPGA code and low-level communication VI's from this example:
https://forums.ni.com/t5/Example-Code/Modbus-Communication-Reference-Example-for-cRIO/ta-p/3996153
In my application i communicate through the NI9871, using the FPGA. The communication seems to work, but i am experiencing some unexpected delays.
The delay seems to appear at the "Wait on IRQ" invoke method in "901x 9871 DMA Read (Sub)" (see attached code). The FPGA code sets this IRQ when the current operation has completed. But i am experiencing unreasonable long delays here. (10+ mS).
I tested it without waiting for the IRQ and this gave me a delay of 1 mS on every attempt. And still i got valid data.
So it seems like the IRQ is held longer than necessarry.
In my application time is critical. The length of the incoming telegrams is fixed.
Thank you for your help.
