Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 133)

Section 7. Installation
133
datalogger, which is displayed by the support software. The CRBasic Editor pre-
compiler returns a similar message.
Note A program can be forced to run in sequential or pipeline modes by placing
the SequentialMode or PipelineMode instruction in the declarations section of
the program.
Some tasks in a program may have higher priorities than other tasks.
Measurement tasks generally take precedence over all others. Priority of tasks is
different for pipeline mode and sequential mode.
Table 15. Task Processes
Measurement Task Digital Task Processing Task
•
Analog
Measurements
•
Excitation
• Read Pulse
Counters
• Read Control
Ports (GetPort())
• Set Control Ports
(SetPort())
•
VibratingWire()
•
PeriodAvg()
• CS616()
• Calibrate()
•
All SDM
instructions, except
SDMSI04() and
SDMI016()
•
Processing
•
Output
•
Serial I/O
• SDMSIO4()
• SDMIO16()
• ReadIO()
• WriteIO()
• Expression evaluation and
variable setting in
measurement and SDM
instructions
7.7.3.6.1 Pipeline Mode
Pipeline mode handles measurement, most SDM, and processing tasks separately,
and possibly simultaneously. Measurements are scheduled to execute at exact
times and with the highest priority, resulting in more-precise timing of
measurement, and usually more-efficient processing and power consumption.
Pipeline scheduling requires that the program be written such that measurements
are executed every scan. Because multiple tasks are taking place at the same time,
the sequence in which the instructions are executed may not be in the order in
which they appear in the program. Therefore, conditional measurements are not
allowed in pipeline mode. Because of the precise execution of measurement
instructions, processing in the current scan (including update of public variables
and data storage) is delayed until all measurements are complete. Some
processing, such as transferring variables to control instructions, like PortSet()
and ExciteV(), may not be completed until the next scan.
When a condition is true for a task to start, it is put in a queue. Because all tasks
are given the same priority, the task is put at the back of the queue. Every 10 ms
(or faster if a new task is triggered) the task currently running is paused and put at