Campbell Scientific CR9000X Measurement and Control System - Manual (Page 346)

Section 9. Program Control Instructions
Parameter
& Data Type Enter SCAN PARAMETERS CON'T
Option Determines how data will be buffered during the Scan…NextScan process.
Constant Option Result
0, 1, or 2 The datalogger uses two buffers when processing
measurements. When a measurement begins on a scan,
the values of the previous scan are loaded into a buffer.
This allows processing to finish on the previous scan
during measurement of the current scan.
>3 The datalogger uses three or more buffers when
processing measurements, based on the number of scans
defined by this Constant.
Larger buffers can be used for a Scan that has occasional large processing
requirements such as FFTs or Histograms, and/or when processing may be
interrupted by communications. If a value of 1000 is inserted into the
BufferSize argument of a scan having 10 thermocouple measurements,
40,000 bytes of SRAM will be allocated for the buffer [(4 bytes)
/(measurement) x (10 measurements)/(buffered scan) x 1000 buffered
scans)]. The buffer size plus the size of any Output Tables stored in SRAM
should not exceed 120 Mbytes.
If the processing ever lags behind by more than the buffer allocated, the
datalogger will discard the buffered values and synchronize back up to the
current measurement
The SlowSequence instruction does not allow for this buffering scheme
even though Scan is used to signify the start of a scan in a slow sequence. In
SlowSequence, the measurements are stored in a single buffer. Processing of
this buffer is completed before the next SlowSequence Scan is started.
The CR9052 module has its own internal memory for buffering up to
8,000,000 samples. The Scan's buffer parameter is used to allocate the
amount of both the CR9052 internal memory and the amount of CR9032
SDRAM to be used for buffering. If using all 6 channels on a CR9052, the
maximum buffer size allowed would be 1,300,000. When using the
CR9052 with scan rates over 1000 Hz, it is recommended to use
SubScans and large scan buffers. See the SubScan topic for more
details.
The CR9058E module also has its own internal memory buffer. It is
limited to 512 buffers. The Scan's buffer parameter is used to allocate the
amount of both the CR9058E internal memory and the amount of CR9032
SDRAM to be used for buffering. If using all 10 channels on a CR9058E,
the maximum buffer size allowed would be 50. If it is desired to run
CR9058E Isolation measurements along with fast measurements and/or with
a larger Scan buffer, SubScans with a negative value for the SubRatio
parameter can be utilized. See the SubScan topic later in this section for
additional information.
Count
Integer The number of times to execute the Scan/NextScan loop. Enter 0 for infinite
looping.
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