tailieunhanh - Microprocessor Interfacing Techniques Lab VIEW Tutorial Part 9

Microprocessor Interfacing Techniques Lab VIEW Tutorial Part 9 | PHY 406 - Microprocessor Interfacing Techniques PHY 406 - Microprocessor Interfacing Techniques LabVIEW Tutorial - Part IX Sequences Sequences LabVIEW works on the concept of dataflow - a function or VI executes when the inputs are available. This is generally OK since we are processing a flow of data but there are occasions when this is not the case. One of the principal areas where we get into trouble is timing. In a typical timing experiment things go like this i. Set up the system ii. Start the clock iii. Send the event trigger iv. Wait for the ending event v. Stop the clock vi. Tidy things up Now we can debate fiercely whether we should start the clock before sending the trigger or aftwerwards but there is a much deeper problem in LabVIEW and that is that there is no obvious dataflow in the pattern. Nothing flows through start the clock to get to send the trigger . These events starting the clock sending the trigger stopping the clock could all occur at very different times and in different sequences but we wish to impose a sequenc on them. In LabVIEW this is the job of the sequence structure. In common with the case structure the sequence structure has a number of panels lying on top of one another. The difference for the sequence function is that they all execute one after the other. We also need a way of transferring information between the panes as well as to the outside world. Communication with the outside world can be made through tunnels which permit a wire to corss the boundary of the sequence. A tunnel can come onto or off any pane but as usual input tunnels can be used in multiple panels and can be ignored at will on other panels whereas output tunnels must have one and only one connection. We also need a way of communicating between panes. This is supplied by a sequence local which is created anywhere on the perimeter of the sequence panel and can then be fed from an output on one panel to input s on other panel s . Sequnce locals are created from