We are routing a signal from FP TrigIn to BP TTLTRG0. This works fine under nominal conditions. However signal polarity through the Slot 0 ctrlr is reversed if ResMan is executed more than once. This results in an equipment hazard and a personal safty issue on our test station. Since ResMan is a standalone application there is no reliable way to block user access to ResMan. The safest solution would be to directly set the signal polarity using a software call (to NI-VXI, etc). This would ensure that polarity is as required even under off-nominal conditions. There are no documented methods to perform polarity control. I am hopeful that you can tell how to set this signal polarity thru a back door or direct register access.
Randal Bailey Systems Engineering 603.885.9254 firstname.lastname@example.org
I assume that you have a vxi-mxi-2 board and want to know if there is a command to set the signal polarity when mapping a signal from the TrigIn to one of the TTL trigger lines on the backplane.
If this is the case, please see the following:
With NI-VXI 2.x, it was possible to inverse the TRIG IN signal internally before mapping it to the TTL trigger line using either TrigExtConfig or MapTrigToTrig. The Trigger Configuration Functions were supported under NI-VXI 2.x, but are no longer supported under NI-VXI 3.0, 3.1, 3.2.
Currently, NI-VXI 3.0, 3.1, 3.2 supports the function MapTrigToTrig() from the NI-VXI API and its NI-VISA equivalent function viMapTrigger. Under NI-VXI 3.2, not all of the features of these two functions are supported. However, in future versions of the NI-VISA and NI-VXI driver, the argument "mode" of the function will be supported. This argument allows to invert the signal that comes from a trigger before mapping it to a TTL tirgger line in the backplane of a VXI chassis.
For more information on trigger mapping and inversion, please see:
How to Map Triggers Using VXI-MXI-2 and NI-VXI 3.0, 3.1, or 3.2: http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/b05466083f58dba686256a9a0070e0c5?OpenDocument
NI-VXI User Manual: http://digital.ni.com/manuals.nsf/websearch/80462709452087E98625665F00700049?OpenDocument&node=132100_US
Unfortunatly the answer appears to NO, there presently is no way to set signal polarity of a signal going thru the slot zero controller (TrigIn to TTLx). I was only persuing this as a work-around anyway. Frankly I would prefer to see ROOT CAUSE of this problem addressed instead.
ROOT CAUSE I would like to reiterate the problem-statement in my first question which I think was missed:
THE EXECUTION OF TWO SUCESSIVE RESMANs CAUSES SIGNAL POLARITY TO REVERSE.
This is a bug. It may seem inconsequencial and easily corrected by a complete system reboot. However in our case this is a dangerous bug which I cannot protect against. This problem is actually forcing us into a redesign to protect human life.
The best solution would be if Trig In polarity DID NOT become indeterminate on a second instance of ResMan.