Campbell Scientific CR3000 CR3000 Micrologger - Page 142

Section 7. Installation allows the processing in the scan to lag behind measurements at times without affecting measurement timing. Use of the CRBasic Editor default size is normal. Refer to section SkippedScan (p. 429) for troubleshooting tips. • Count - number of scans to make before proceeding to the instruction following NextScan. A count of 0 means to continue looping forever (or until ExitScan). In the example in CRBasic example Scan Syntax (p. 141), the scan is 1 second, three scans are buffered, and measurements and data storage continue indefinitely. 7.7.3.7.2 SlowSequence / EndSequence Slow sequences include automatic and user entered sequences. Background calibration is an automatic slow sequence. User-entered slow sequences are declared with the SlowSequence instruction and run outside the main-program scan. They typically run at a slower rate than the main scan. Up to four slow-sequences scans can be defined in a program. Instructions in a slow-sequence scan are executed when the main scan is not active. When running in pipeline mode, slow-sequence measurements are spliced in after measurements in the main program, as time allows. Because of this splicing, measurements in a slow sequence may span across multiple-scan intervals in the main program. When no measurements need to be spliced, the slow-sequence scan will run independent of the main scan, so slow sequences with no measurements can run at intervals ≤ main-scan interval (still in 10-ms increments) without skipping scans. When measurements are spliced, checking for skipped slow scans is done after the first splice is complete rather than immediately after the interval comes true. In sequential mode, all instructions in slow sequences are executed as they occur in the program according to task priority. Background calibration is an automatic, slow-sequence scan. Read More! Self-Calibration (p. 295) 7.7.3.7.3 SubScan() / NextSubScan SubScan() / NextSubScan are used in the control of analog multiplexers (see the appendix Analog Multiplexers (p. 562) for information on available analog multiplexers) or to measure analog inputs at a faster rate than the program scan. SubScan() / NextSubScan can be used in a SlowSequenc / EndSequence with an interval of 0. SubScan cannot be nested. PulseCount or SDM measurement cannot be used within a sub scan. 7.7.3.7.4 Scan Priorities in Sequential Mode Note Measurement tasks have priority over other tasks such as processing and communication to allow accurate timing needed within most measurement instructions. A priority scheme is used in sequential mode to avoid conflicting use of measurement hardware. As illustrated in figure Sequential-Mode Scan Priority Flow Diagrams (p. 144), the main scan sequence has the highest priority. Other sequences, such as slow sequences and calibration scans, must wait to access 142