Campbell Scientific CR10 CR10 Measurement and Control - Page 54

SECTION 3. INSTRUCTION SET BASICS As an example, suppose it is desired to obtain a wind speed rose incorporating only wind speeds greater than or equal to 4.5 m/s. The wind speed rose is computed using the Histogram Instruction 75, and wind speed is stored in input location 14, in m/s. lnstruction 89 is placed just before Instruction 75 and is used to set Flag 9 high if the wind speed is less than 4.5 m/s: TABLE 3.7-2. Example of the Use of Flag 9 Inst. Param. Loc. No. Entrv Description X P89 't 14 lf wind speed < 4.5 m/s Wind speed location 24 Comparison: < 3 4.5 Minimum wind 419 X+1 P75 X+2 P86 speed for histogram Set Flag t high Histogram Do Set Flaq 9 Low NOTE: Flag 9 is automatically reset the same as Flag 0. lf the intermediate processing disable flag is already set high and the test condition of a subsequent Program Control lnstruction acting on Flag 9 fails, the flag is set low. This feature eliminates having to enter another instruction to specifically reset Flag 9 before proceeding to another group of test conditions. 3.7.3 USER FLAGS Flags 1-8 are not dedicated to a specific purpose and are availabb to the user for general programming needs. The user flags can be manually toggled from the keyboard in the *6 Mode (Section 1.3). By inserting the flag test (lnstruction 91) at appropriate points in the program, the user can use the "6 Mode to manually direct program execution. 3.8 PROGRAM CONTROL LOGICAL coNsTRucTroNs Most of the Program Control Instructions have a command code parameter which is used to specify the action to be taken if the condition tested in the instruction is true. Table 3.8-1 lists these codes. TABLE 3.&1. Command Godes 0 1-9,79-99 10-19 20-29 30 31 32 41-48 51-58 61-68 71-78 - Go to end of program table - Call Subroutine 1-9, 79-991 Set Flag 0-9 high Set Flag 0-9low Then Do Exit loop if true Exit loop if false Set Port 1-8 nignz Set Port 1-8low2 Toggle Port 1-82 Pulse Port 1-82 1 97 and 98 are specialsubroutines which can be called by Control ports 7 and 8 going high; see lnstruction 85 for details. 2 Ports can be indexed to the loop counter 3.8.1 IF THEN/ELSE COMPARISONS Program Control Instructions can be used for lf then/else comparisons. When Command 30 fihen do) is used with Instructions 83 or 88-92, the lf Instruction is followed immediately by instructions to execute if the comparison is true. The Else Instruction (94) is optionaland is followed by the instructions to execute if the comparison is false. The End Instruction (95) ends the lf then/else comparison and marks the beginning of the instructions that are executed regardless of the outcome of the comparison (see Figure 3.8-1). rF (83 OR 88-92 WrTH COMMAN o) I TRUE ELSI (e4) FALSE I END (es) + FIGURE 3.8-1. lf Then/Else Execution Sequence 3-4