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NI 9871 Deploy option error

I am using cRIO-9068 Chassis with NI 9871 detected in scan mode (other modules are in FPGA mode).

Able to see the ports in NI MAX as ASRL::4 to ASRL::7

I am facing issue with communicating with the ports, like unable to open/close the port using Modbus master vi's (shown in NI 9871.jpg)


I followed steps, mentioned in below link and ran through error

Discover, Configure, and Communicate with NI 987x Modules in Scan Mode-


Error was : "The current module settings require NI Scan Engine support on the controller. You can use Measurement & Automation Explorer (MAX) to install a recommended software set of NI CompactRIO with NI Scan Engine support on the controller. If LabVIEW FPGA is installed, you can use this module with LabVIEW FPGA by adding an FPGA Target item under the chassis, and drag and drop the module onto the FPGA Target item." (see attached Discover Communicate .JPG)


I reinstall the Scan Engine Support software tool using NI MAX and couldn't solve the issue, I performed clearing all the software and reinstalled everything and couldn't solve the issue. when I try to deploy NI 9871,  I see the same error popping up.


I need to configure NI 9871 as scan resource and should be able to access the ports. please suggest

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i have reinstalled all the software in the cRIO based on the solution given below


I'm seeing + symbol for the all the software list. what could be the difference?




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Hi phanihalliburton,


Thanks for reaching out- sorry you are having issues. The first thing I'm wondering is if you have the Scan Engine installed on your cRIO? Secondly, when you reinstalled the software, did you format the target first?


Let me know.

Keddy C.
Technical Support Engineer
National Instruments
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I did "uninstall all software" first as shown below. is this the formatting?



yes, Scan Engine 7.0 is installed.




Even though, I am unable to deploy NI 9871. I am able to see the ports in NIMAX, Host VI and RT in VISA Resource List as shown below





I have add 120 ohm termination resistor at both the ends as mentioned in "Figure 5. 2-Wire Multidrop Network Using Terminating Resistors" of NI 9871 - GETTING STARTED GUIDE pdf

I am able to open and close the port using modbus master create instance and Close the instance in RT Compact RIO Target without any error, as shown below

but when i try to read any holding registers, i get Error 56 "SubVIs.lvlib:RTU Data Unit.lvclass:Read ADU"



Do I need to resolve the deployment error first ?

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I'm having a similar issue where the NI9871(with ext power) is not showing the ports even with NI-Scan Engine installed.


While searching the NI site I found a specified that the NI-Serial 9870 and 9771 Scan Engine Support.  However, when I try to install it comes up with a pop-up window saying that NI-RIO IO Scan 14.0 is not installed.  IO Scan is also not on the list of available software for install.   


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