Campbell Scientific CR9000X Measurement and Control System - Manual (Page 351)

Section 9. Program Control Instructions
(settling time + A/D conversion) from the scan in the slow sequence. In the
case where the primary scan interval is only long enough to allow one
measurement fragment from the slow sequence per primary scan, the minimum
time for the slow sequence scan interval is the product of the number of slow
sequence measurement segments and the primary scan interval. A
consequence of the way a measurement scan in the slow sequence may be
parceled into several primary scans is that the measurements in a single "scan"
of the slow sequence may be spread over a greater time than if they were in the
primary scan. Also, if integration is used in a measurement that is included in
the SlowSequence scan, the measurements that go into that integration may
not occur sequentially, but may be broken up into multiple integration
segments that are separated in time by the primary scan rate. If settling time is
used for a measurement whose integration is broken up, that settling time will
take place before each integration period. Processing instructions within the
slow sequence are executed in the time available after processing in the main
program is completed.
The slowest scan rate allowed is 60 seconds. When making multiple
measurements in the SlowSequence scan along with a small scan rate ratio,
[Slow Sequence Scan Time]/[Primary Scan Time], it is possible that all of the
slow sequence tasks will not fit within the task sequencer's memory. When this
occurs, the error message "Program too big for task memory" will be returned
when attempting to load the program into the datalogger's flash memory. This
can be resolved by increasing the primary scan rate, so that the instructions in
the slow sequence scan can be parceled out to the task sequencer throughout
one or more primary scans. The required scan rate ratio is dependent on the
number of tasks in the SlowSequence scan.
Low priority data tables can be included in the slow sequence scan by listing
them after the SlowSequence instruction. It should be noted that time stamped
data written to slow sequence data tables will be stamped with the start time of
the last slow sequence scan.
TimeSlice
The TimeSlice parameter is used to adjust the size or number of operational
codes in the segments parceled from the SlowSequence Scan. Enter 0 for
default slicing. Enter a positive number to decrease the segment size from the
default. Enter a negative number to increase the segment size.
If the SlowSequence scan is skipping scans (check the Status Table to verify),
decrease the TimeSlice parameter incrementally by the value of the Primary
Scan interval, in microseconds, divided by 10 until scans are no longer being
skipped. The minimum TimeSlice value that should be used is -1.8 times the
Primary Scan interval.
Example: If the Primary Scan rate is 10 mSec and SlowSequence scans are
being skipped, change the TimeSlice parameter to -1000 (10,000
microseconds/10) from zero. If skipped SlowSequence scans are still
occurring, change the TimeSlice parameter to -2000, then -3000, and so on,
down to negative 1.8 times the Primary scan (-18,000 for this example). If
skipped SlowSequence scans still occur with the TimeSlice parameter set to -
1.8 times the Primary scan interval, then the SlowSequence scan interval
should be increased.
If the Primary Scan is having skipped scans, then comment out the Slow
Sequence section and check whether skipped scans are still occurring. If there
are skipped scans without the SlowSequence scan, then the Primary Scan
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