my computer can not talk with the Dynisco UPR 700 through RS485.

[serf408]

I used two wire connection for the serial instrument. there is an error information:
Possible reason(s):

VISA: (Hex 0xBFFF0072) The resource is valid, but VISA cannot currently access it.

[Chris_Rake]

Sounds like the COM port is already open by another application (like Hyperterm?).