Campbell Scientific CR1000KD CR1000 Measurement and Control System - Page 136

Section 7. Installation Table 17. Program Timing Instructions Instructions General Guidelines SubScan / NextSubScan Use when measurements or processing must run at faster frequencies than that of the main program. Syntax Form BeginProg Scan() '. '. '. SubScan() '. '. '. NextSubScan NextScan EndProg 7.7.3.7.1 Scan() / NextScan Simple CR1000 programs are often built entirely within a single Scan() / NextScan structure, with only variable and data-table declarations outside the Scan() / NextScan structure. In these simple programs, Scan() / NextScan creates an infinite loop, each periodic pass through the loop being synchronized to the CR1000 clock. Scan() parameters allow modification of the period in 10- ms increments. As shown in CRBasic example BeginProg / Scan() / NextScan / EndProg Syntax (p. 136), aside from declarations, the CRBasic program may be relatively short. CRBasic Example 15. BeginProg / Scan() / NextScan / EndProg Syntax BeginProg Scan(1,Sec,3,0) PanelTemp(RefTemp, 250) TCDiff(TC(),6,mV2_5C,1,...) CallTable Temp NextScan EndProg Scan() determines how frequently instructions in the program are executed, as shown in CRBasic example Scan Syntax (p. 136): CRBasic Example 16. Scan Syntax 'Scan(Interval, Units, BufferSize, Count) Scan(1,Sec,3,0) · · · ExitScan Scan() has four parameters: • Interval - the interval between scans. • Units - the time unit for the interval. Interval is 10 ms