Campbell Scientific CR9000X Measurement and Control System - Manual (Page 136)

Section 4. CRBasic – Native Language Programming
The structure of a CRBasic program requires that variables and subroutines be
defined before they can be used. The best way to do this is to put all the
variable declarations and output table definitions at the beginning, followed by
the subroutines, and then the program. Table 4.2.3-1 describes the structure of
a typical CR9000X program. Example Program 4.2.3-1 and 4.2.3-2 show
examples of following correct program structure.
TABLE 4.2.3-1: Program Structure
Declarations Define datalogger memory usage. Declare constants, variables,
aliases, units, and data tables.
Declare constants Declare fixed constant variables to their values
Declare Public variables Declare & dimension Public Variables(variables that will be
viewable using real-time monitoring during program execution)
Dimension variables Declare & dimension variables not viewable during program
execution.
Define Aliases Assign aliases names to variables.
Define Units Assign engineering units to variable (optional). Units are strictly for
documentation. The CR9000X makes no use of Units nor checks
Unit accuracy.
Define data tables. Describe, in detail, stored data tables.
Process/store trigger Set when the data should be stored. Are they stored when some
condition is met? Are data stored on a fixed interval? Are they
stored on a fixed interval only while some condition is met?
Table size Set the size of the table in CR9000X RAM
Other on-line storage devices Should the data also be sent to PC card or Flash memory?
Processing of Data What data are to be output (current value, average, maximum,
minimum, etc.)
Define Subroutines If there is a process or series of calculations that need to be repeated
several times in the program, it can be packaged in a subroutine
and called when needed rather than repeating all the code each
time. Can include measurement Scans for conditional
measurements
Begin Program BeginProgram defines the beginning of the statements that define
datalogger actions
Set scan interval The Scan instruction sets the interval for a series of measurements
Measurements Enter the measurements to make
Processing Enter any additional processing
Initiate controls Check measurements and Initiate controls if necessary
Call Data Table(s) Declared Data Tables must be called to process and store data
NextScan Loop back (and wait if necessary) for the next scan
End Program
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