Chapter 4 Signal ConnectionsPCI-6023E/6024E/6025E User Manual4-32 ©National Instruments Corporationwill depend upon the particular timing signal being controlled. Thedetection requirements for each timing signal are listed within the sectionthat discusses that individual signal.In edge-detection mode, the minimum pulse width required is 10 ns. Thisapplies for both rising-edge and falling-edge polarity settings. There is nomaximum pulse-width requirement in edge-detect mode.In level-detection mode, there are no minimum or maximum pulse-widthrequirements imposed by the PFIs themselves, but there may be limitsimposed by the particular timing signal being controlled. Theserequirements are listed later in this chapter.DAQ Timing ConnectionsThe DAQ timing signals are SCANCLK, EXTSTROBE*, TRIG1, TRIG2,STARTSCAN, CONVERT*, AIGATE, and SISOURCE.Posttriggered data acquisition allows you to view only data that is acquiredafter a trigger event is received. A typical posttriggered DAQ sequence isshown in Figure 4-17. Pretriggered data acquisition allows you to view datathat is acquired before the trigger of interest in addition to data acquiredafter the trigger. Figure 4-18 shows a typical pretriggered DAQ sequence.The description for each signal shown in these figures is included later inthis chapter.Figure 4-17. Typical Posttriggered Acquisition13 04 2TRIG1STARTSCANCONVERT*Scan Counter
