Campbell Scientific CR23X Micrologger - Manual (Page 19)

CR23X MICROLOGGER OVERVIEW
OV-9
Each instruction in the table requires a finite
time to execute. If the execution interval is less
than the time required to process the table, an
execution interval overrun (table overrun)
occurs; the CR23X finishes processing the
table and waits for the next execution interval
before initiating the table. When a table
overrun occurs,
T
o
appears in the lower right
corner of the display in the Running Table
mode
(
0 ). Overruns and table priority are
discussed in Section 1.1.
OV2.2.2. THE OUTPUT INTERVAL
The interval at which output occurs must be an
integer multiple of the execution interval (e.g., a
table cannot have a 10 minute execution
interval and output every 15 minutes).
A single program table can have many different
output intervals and conditions, each with a
unique data set (Output Array). Program
Control Instructions are used to set the Output
Flag. The Output Processing Instructions
which follow the instruction setting the Output
Flag determine the data output and its
sequence. Each additional Output Array is
created by another Program Control Instruction
checking a output condition, followed by Output
Processing Instructions defining the data set to
output.
OV2.3 CR23X INSTRUCTION TYPES
Figure OV2.3-1 illustrates the use of three
different instruction types which act on data.
The fourth type, Program Control, is used to
control output times and vary program
execution. Instructions are identified by
numbers.
1. INPUT/OUTPUT INSTRUCTIONS (1-29,
100-110, 113-118, 130-134; Section 9)
control the terminal strip inputs and outputs
(Figure OV1.1-2), storing the results in
Input Storage (destination). Multiplier and
offset parameters allow conversion of linear
signals into engineering units. The Digital
I/O Ports and CAO analog output ports are
also addressed with I/O Instructions.
2. PROCESSING INSTRUCTIONS (30-68,
Section 10) perform numerical operations
on values located in Input Storage and
store the results back in Input Storage.
These instructions can be used to develop
high level algorithms to process
measurements prior to Output Processing.
3. OUTPUT PROCESSING INSTRUCTIONS
(69-82, Section 11) are the only
instructions which store data in Final
Storage. Input Storage values are
processed over time to obtain averages,
maxima, minima, etc. There are two types
of processing done by Output Instructions:
Intermediate and Final.
Intermediate processing normally takes
place each time the instruction is executed.
For example, when the Average Instruction
is executed, it adds the values from the
input locations being averaged to running
totals in Intermediate Storage. It also keeps
track of the number of samples.
Final processing occurs only when the
Output Flag is high (Section 3.7.1). The
Output Processing Instructions check the
Output Flag. If the flag is high, final values
are calculated and output. With the
Average, the totals are divided by the
number of samples and the resulting
averages sent to Final Storage.
Intermediate locations are zeroed and the
process starts over. The Output Flag, Flag
0, is set high by a Program Control
Instruction which must precede the Output
Processing Instructions in the user entered
program.
4. PROGRAM CONTROL INSTRUCTIONS
(83-98, 111, 120-123, 220; Section 12) are
used for logic decisions, conditional
statements, and to send data to peripherals.
They can set flags and ports, compare
values or times, execute loops, call
subroutines, conditionally execute portions
of the program, etc.