DIO 6534 input/output setup

[YJ2003]

I am using two PCI6534 to do some memory test.The test system will run at 20MHz with Pattern IO mode. I use the card1 to write 16-bit data as 0011001100110011 to the memoryDUT, then use the card2 to read the 16-bit data out. The problem I met is, because both the output data lines in card1 and input data lines in card2 are connected with the data bus lines of memoryDUT together, I do not know how to read the data from the memoryDUT (because the result might be the output data of card1 ...)? The only way seems that I have to set the 16-bit data lines in card1 as high impedance during the data-reading process of card2. Could you tell me if it is possible to setup the output lines with three states,low0,high1 and high impedance? Is the 16-bit in
put lines of card2 always in high impedance before I run the DIO read block whenever the input is? Or could you give me some other suggestion? Desperately need help:( Thanks in advance.

[RIO-Todd]

This would be tri-state mode, which the NI 653x devices support. You can programmatically set the 653x device to use tri-state mode by using the DIG_Prt_Config function and changing the dir (direction) parameter to 3, but you can only use tri-state mode in unstrobed (non-clocked) I/O operation. Since you are performing pattern I/O, this option won't be available. Take a look at the links below for additional information. I hope this helps.

What Is Tri-State and Which DAQ Devices Support It?
http://digital.ni.com/public.nsf/websearch/09B559BE292C75DB8625698500640E0A?OpenDocument

Introduction to Wired-OR Outputs and Open-Collector Circuits
http://zone.ni.com/devzone/conceptd.nsf/webmain/9739E26BBE06286586256C3A007A7839?opendocument

653X User Manual
http:
//digital.ni.com/manuals.nsf/caba5d53e9b015a186256793004eebb7/ede443f5c700373a862569b90072d26f

Regards,

Todd D.
National Instruments
Applications Engineer