Problem: Using a 9073 chassis with mixed I/O and both FPGA and Scan Engine, excitation voltage for a 9237 module (in Scan Engine) would not change from the apparent default of 2.5VDC, although the module was properly deployed for 10VDC excitation from the LabVIEW project. LabVIEW version 8.6.1.
Work around: From the RT application, during application start, add an approximate 5 second delay BEFORE calling the FPGA startup.
Background:
Previous use of the 9237 with Scan Engine ONLY had NOT proposed any problems with the 9237 excitation being set based upon the chassis deployment. However, in this application, a mixed system using both Scan Engine (where the 9237 resides) and FPGA, the excitation would not change from 2.5VDC. This was a no load condition on the excitation, therefore a power limiting issue should NOT be present.
After further investigation and setting the 9073 to Scan Engine only and redeploying, the excitation voltage from the 9237 immediately changed to 10VDC. After setting the chassis to FPGA and redeploying, the excitation remained at 10VDC UNTIL THE CHASSIS WAS RESTARTED. At that point the excitation returned to 2.5VDC.
Recognizing this as a potentianl race condition between the Scan Engine and FPGA, I updated the RT application to execute a 5 second wait on initialization BEFORE the FPGA was called.
