Campbell Scientific CR3000 CR3000 Micrologger - Page 151

Section 7. Installation TRUE is safe, it may not always be the best programming technique. Consider the expression If Condition(1) then... Since = True is omitted from the expression, Condition(1) is considered true if it equals any non-zero value. Table 21. Binary Conditions of TRUE and FALSE Condition CRBasic Instruction(s) Used Memory Location of Binary Result Time TimeIntoInterval() Variable, System IfTime() Variable, System Control Port Trigger WaitDigTrig() System Communications VoiceBeg() System ComPortIsActive() Variable PPPClose() Variable Measurement Event DataEvent() System Using TRUE or FALSE conditions with logic operators such as AND and OR, logical expressions can be encoded to perform one of the following three general logic functions. Doing so facilitates conditional processing and control applications: 1. Evaluate an expression, take one path or action if the expression is true (= -1), and / or another path or action if the expression is false (= 0). 2. Evaluate multiple expressions linked with AND or OR. 3. Evaluate multiple AND or OR links. The following commands and logical operators are used to construct logical expressions. CRBasic example Logical Expression Examples (p. 151) demonstrate some logical expressions. • IF • AND • OR • NOT • XOR • IMP • IIF Table 22. Logical Expression Examples If X >= 5 then Y = 0 Sets the variable Y to 0 if the expression "X >= 5" is true, i.e. if X is greater than or equal to 5. The CR3000 evaluates the expression (X >= 5) and registers in system memory a -1 if the expression is true, or a 0 if the expression is false. If X >= 5 OR Z = 2 then Y = 0 Sets Y = 0 if either X >= 5 or Z = 2 is true. 151