Campbell-scientific CR9000X Measurement and Control System Manual de usuario descargar pdf (Pagina 135)

Section 4. CRBasic – Native Language Programming

Keywords and predefined constants are reserved for internal

CR9000X use. If a user programmed variable happens to be a

keyword or predefined constant, a runtime or compile error will

occur. To correct the error, simply change the variable. CRBasic

Help also has the list of keywords and pre-defined constants.

NOTE

See Appendix A Keywords and Predefined Constants for a list of keywords

and pre-defined constants.

• Common instructions – Instructions and operators used in most BASIC

languages, including program control statements, and logic and

mathematical operators.

• Special instructions – Instructions unique to CRBASIC, including

measurement instructions that access measurement channels, and

processing instructions that compress many common calculations used in

CR9000X dataloggers.

These four elements must be properly placed within the program structure.

4.2.2 Numerical Entries

In addition to entering regular base 10 numbers there are 3 additional ways to

represent numbers in a program: scientific notation, binary, and hexadecimal

(Table 4.2.2-1).

TABLE 4.2.2-1 Formats for Entering

Numbers in CRBasic

Format Example Base10 Value

Standard 6.832 6.832

Scientific notation 5.67E-8 5.67X10

-8

Binary: &B1101 13

Hexadecimal &HFF 255

The binary format makes it easy to visualize operations where the ones and

zeros translate into specific commands. For example, a block of ports can be

set with a number, the binary form of which represents the status of the ports

(1= high, 0=low). To set ports 1, 3, 4, and 6 high and 2, 5, 7, and 8 low; the

number is &B00101101. The least significant bit on the right represents port 1.

This is much easier to visualize than entering 72, the decimal equivalent.

4.2.3 Programming Structure

A typical CRBasic program contains:

a) Variable Declarations

b) Data Table Definitions

c) Subroutine Definitions (The use of subroutines is optional)

d) Program(s) including the Scan Interval, Measurements, Processes, Controls, and calls to

Data Tables

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