Visa com ports in ni max

[Manik981211]

I'm using 18 slots ni pxie 8840 RT controller. In that i inserted some RS232 and RS485 Pxie cards. Here the problem is except two serial cards I couldn't find visa ports in the ni max. First when I inserted all cards, only slot 2 and 11 com ports were only visible. Then I removed slot card from slot 2.Then it shown slot 10 and 11 only. Afterwards I removed card from slot 11 also. Then it shown only slot 9 and 10 in MAX. 

I couldn't able to understand why it is happening like this.

[ZYOng · Accepted solution]

From Detect More Than Four Serial Ports in Linux Desktop

The kernel for NI Linux Real Time is pre-configured to allow up to 32 serial ports, when being used with NI-Serial 20.0 or earlier. The switch away from the 8250 driver as base for NI-Serial was already with NI-Serial 21.3 on NI LInux RT. So, if you need more than 32 serial ports based on 843x in Linux RT, update your NI Linux RT System Image to version  21.3 or newer.