Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 133
Pipeline Mode
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Section 7. Installation 7.7.3.6.1 Pipeline Mode datalogger, which is displayed by the support software. The CRBasic Editor precompiler returns a similar message. Note A program can be forced to run in sequential or pipeline modes by placing the SequentialMode or PipelineMode instruction in the declarations section of the program. Some tasks in a program may have higher priorities than other tasks. Measurement tasks generally take precedence over all others. Priority of tasks is different for pipeline mode and sequential mode. Table 15. Task Processes Measurement Task Digital Task Processing Task • Analog Measurements • Excitation • Read Pulse Counters • All SDM • Processing instructions, except SDMSI04() and • Output SDMI016() • Serial I/O • SDMSIO4() • Read Control Ports (GetPort()) • Set Control Ports (SetPort()) • VibratingWire() • PeriodAvg() • CS616() • SDMIO16() • ReadIO() • WriteIO() • Expression evaluation and variable setting in measurement and SDM instructions • Calibrate() Pipeline mode handles measurement, most SDM, and processing tasks separately, and possibly simultaneously. Measurements are scheduled to execute at exact times and with the highest priority, resulting in more-precise timing of measurement, and usually more-efficient processing and power consumption. Pipeline scheduling requires that the program be written such that measurements are executed every scan. Because multiple tasks are taking place at the same time, the sequence in which the instructions are executed may not be in the order in which they appear in the program. Therefore, conditional measurements are not allowed in pipeline mode. Because of the precise execution of measurement instructions, processing in the current scan (including update of public variables and data storage) is delayed until all measurements are complete. Some processing, such as transferring variables to control instructions, like PortSet() and ExciteV(), may not be completed until the next scan. When a condition is true for a task to start, it is put in a queue. Because all tasks are given the same priority, the task is put at the back of the queue. Every 10 ms (or faster if a new task is triggered) the task currently running is paused and put at 133