Campbell CR800 Series, Operator'S Manual

Page: 153 / 598

Section 7. Installation
153
7.6.3.13 Execution Timing
Timing of program execution is regulated by timing instructions listed in the
following table.
Program Timing Instructions
Instructions General Guidelines Syntax Form
Scan() / NextScan
Use in most programs.
Begins / ends the main
scan.
BeginProg
Scan()
'.
'.
'.
NextScan
EndProg
SlowSequence /
EndSequence
Use when measurements
or processing must run
at slower frequencies
than that of the main
program.
BeginProg
Scan()
'.
'.
'.
NextScan
SlowSequence
Scan()
'.
'.
'.
NextScan
EndSequence
EndProg
SubScan /
NextSubScan
Use when measurements
or processing must run
at faster frequencies
than that of the main
program.
BeginProg
Scan()
'.
'.
'.
SubScan()
'.
'.
'.
NextSubScan
NextScan
EndProg
7.6.3.13.1 Scan() / NextScan
Simple CR800 programs are often built entirely within a single Scan() /
NextScan structure, with only variable and data-table declarations outside the
scan. Scan() / NextScan creates an infinite loop; each periodic pass through the
loop is synchronized to the CR800 clock.
Scan()
parameters allow modification
of the period in 10 ms increments up to 24 hours. As shown in CRBasic example
BeginProg / Scan() / NextScan / EndProg Syntax
(p. 153),
the CRBasic program
may be relatively short.