Program Control Logical Constructions; If Then/Else Execution Sequence - Campbell Measurement and Control Module CR10 Operator's Manual

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. Instruction
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. Entry
X P 89
1 14
2
3
4 19
X+1 P 75
X+2 P 86
1 29
NOTE: Flag 9 is automatically reset the
same as Flag 0. If the intermediate
processing disable flag is already set high
and the test condition of a subsequent
Program Control Instruction 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 available 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 (Instruction 91) at appropriate points in the
program, the user can use the *6 Mode to
manually direct program execution.
3.8 PROGRAM CONTROL LOGICAL
CONSTRUCTIONS
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.
3-4
Description
If wind speed < 4.5 m/s
Wind speed location
4 Comparison: <
4.5 Minimum wind
speed for histogram
Set Flag 9 high
Histogram
Do
Set Flag 9 Low
TABLE 3.8-1. Command Codes
0 - Go to end of program table
1-9, 79-99 - Call Subroutine 1-9, 79-99
10-19 - Set Flag 0-9 high
20-29 - Set Flag 0-9 low
30 - Then Do
31 - Exit loop if true
32 - Exit loop if false
41-48 - Set Port 1-8 high
51-58 - Set Port 1-8 low
61-68 - Toggle Port 1-8
71-78 - Pulse Port 1-8
1
97 and 98 are special subroutines which can
be called by Control ports 7 and 8 going high;
see Instruction 85 for details.
2
Ports can be indexed to the loop counter
(Section 3.4).
3.8.1 IF THEN/ELSE COMPARISONS
Program Control Instructions can be used for If
then/else comparisons. When Command 30
(Then do) is used with Instructions 83 or 88-92,
the If Instruction is followed immediately by
instructions to execute if the comparison is true.
The Else Instruction (94) is optional and is
followed by the instructions to execute if the
comparison is false. The End Instruction (95)
ends the If 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).
FIGURE 3.8-1. If Then/Else
Execution Sequence
1
2
2
2
2