Timed Loops in Embedded Module for Blackfin Processors are different than LabVIEW Base, Full, Pro Primary Software: LabVIEW Modules>>Embedded Module for Blackfin ProcessorsPrimary Software Version: 1.0 Primary Software Fixed Version: N/A Secondary Software: N/A
Problem: The Configure Timed Loop dialog box in the Embedded Module for Blackfin Processors doesn't have as many options as the same dialog box in LabVIEW Base, Full, or Pro. Why? Solution: Blackfin VIs support the Timed Loop differently than VIs you create for Windows. When you are creating a Blackfin VI, the Configure Timed Loop dialog box shows only those options that are supported on the Blackfin target. If you click the Help button in the dialog box, the help topic includes options that are unsupported for the Blackfin target. Blackfin VIs support the following Timed Loop configuration options: Use Built-In Timing Source—Specifies an internal timing source from the Source Type listbox to control the timed structure. Blackfin VIs support a 1 kHz or 1 MHz timing source. Using the 1 kHz clock, a timed structure can execute an iteration once every 1 millisecond. Using the 1 MHz clock, a timed structure can execute an iteration once every 1 microsecond. Source name—Specifies the name for the instance of the timing source. Use Timing Source Terminal—Specifies to use the input terminal on the Input Node to wire an external timing source. You must select this option to enable the Advanced Timing options. You can use the Create External Timing Source VI to control a Timed Loop with external events, such as Interrupts, rather than a clock timing source. Period—Specifies the amount of time that elapses between two subsequent iterations of the Timed Loop. The unit of the period changes depending on the timing source you select in Source Type. Priority—Specifies the priority of the execution of the timed structure relative to other structures that are ready to execute. The higher the number you enter, the higher the priority of the timed structure over other structures. Blackfin VIs support a priority range of 1-30 with 26 being the default. Note: The default priority that shows in the dialog box is 100, but the default is really 26. If you use the 1 MHz clock, the valid range is 27-30. Timeout—Specifies the maximum amount of time, in milliseconds, the Timed Loop can wait for a trigger event from the timing source. If the Timed Loop does not begin to execute before the timeout value, the Timed Loop executes the iteration untimed and returns Timeout in the Wake-up reason output on the Left Data node in the next iteration. If a Timed Loop times out and no changes are made to the Offset or Period inputs on the Right Data node, the Timed Loop waits on the next iteration at the same point where the original time out occurred for the same wake-up event. You must select Use Timing Source Terminal or wire something to the Source Name to enable this option. Offset / Phase—Specifies the starting time or phase for the iteration of the structure. You can use this option to synchronize structures or align their phases. For example, you can configure two Timed Loops to use the same timing source instance by specifying the same name in Source name. In one Timed Loop, you can enter a value of 0 in Offset / Phase and in the other Timed Loop enter a value of 100. The Timed Loops execute at their respective periods, but 100 timing units separate their execution. You must select Use Timing Source Terminal or wire something to the Source Name to enable this option. Related Links: Attachments:
Report Date: 02/09/2007 Last Updated: 02/12/2007 Document ID: 468E2SKN |
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