Can I tristate a com port in 8423 card?

Hi all
Am using 2 PXI 8186 to send commands to some COM based devices through a single RS485, 4 wire bus, but it is not possible to send commands to the device from both the PXI's. Only if one PXI is switched off the other PXI is able to send commands, i belive this is happening because both the PXI's are trying to take control of the bus. I wanted to know if there is a way in which i can tristate one of the PXI's com port so that other PXI can send the commands on the bus.
Thanx for the reply
Arun

Hi Emilie
I have two 1031 PXI chassis, both the chassis have two 8423 cards (with four RS485 ports) and a PXI 8186. both the PXI have to comunicate with COM devices. the block diagram is attached along with this mail. my problem is if both the PXI's are switched on they don't communicate with the devices, only one of them can take control of the bus ata time, so i wanted to know if there is away in which i can place the com ports in 8423 cards in tristate.
Thanx for the reply
regards
Arun
Attachments:
conection.JPG ‏27 KB

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由 jw2002 在 06-28-2009 09:20 AM
上編輯的訊息
由 jw2002 在 06-28-2009 09:20 AM
上編輯的訊息
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