National Instruments PCI-8430 - Page 93

PerformanceonLabVIEWReal-Time
NI-SerialusersonLabVIEWReal-Timehavecontroloverwhether
secondaryinterrupthandlingisenabled.Whensecondaryinterrupt
handlingisenabled,I/Oisprocessedataprioritylowerthantime-critical.
Usingsecondaryinterrupthandlingreducesjitterfortime-criticalloops
andmakesserialhardwareinterruptsmoredeterministic.However,it
mayalsoreduceI/Operformanceandcanincreasethepossibilityof
overflowingtheRXFIFObuffer.Secondaryinterrupthandlingisasetting
atthesystem-widelevelandisenabledbydefault.
Toenableordisablethisfeature,completethefollowingsteps:
1. Copytoyourhosttheniserial.dbsfileinthe/ni-rt/systemdirectory
ontheRTtarget.
2. Intheniserial.dbsfile,findtheentrySecondaryInterruptsand
modifyitaccordingly:
Toenablesecondaryinterrupthandling,set
SecondaryInterruptsto1.
Todisablesecondaryinterrupthandling,set
SecondaryInterruptsto0.
3. Downloadtheupdatedniserial.dbsfiletothetarget,overwritingthe
existingfileinthe/ni-rt/systemdirectory.
4. RebootyourRTtarget.