Campbell Scientific CR6 CR6 Measurement and Control System - Page 208

TableFile with Option 64 Q &

Page 208 highlights

Section 7. Installation Public Sensor(10) DataTable(Ts_data,TRUE,-1) 'TableFile("filename",Option,MaxFiles,NumRec/TimeIntoInterval,Interval,Units, ' OutStat,LastFileName) TableFile("CRD:"&Status.SerialNumber(1,1)&".ts_data_",64,-1,0,1,Day,0,0) Sample(10,sensor(1),IEEE4) EndTable BeginProg Scan(100,mSec,100,0) 'Measurement instructions go here. 'Processing instructions go here. CallTable ts_data NextScan EndProg 7.9.11.4 TableFile() with Option 64 Q & A Q: How does Option 64 differ from other TableFile() options? A: Pre-allocation of memory combines with TOB3 data format to give Option 64 two principal advantages over other TableFile() options. These are: • increased runtime write performance • short card eject times Option 64 is unique among table file options in that it pre-allocates enough memory on the memory card to store an interval amount of data1. Pre-allocation allows data to be continuously and more quickly written to the card in ≈1 KB blocks. TOB3 binary format copies data directly from CPU memory to the memory card without format conversion, lending additional speed and efficiency to the data storage process. Note Pre-allocation of memory card files significantly increases run time write performance. It also reduces the risk of file corruption that can occur as a result of power loss or incorrect card removal. Note To avoid data corruption and loss, memory card removal must always be initiated by pressing the Eject button on the face of the CR6. The card must be ejected only after the Act light shows a solid green. Q: Why are individual files limited to 2 GB? A: In common with many other systems, the datalogger natively supports signed four-byte integers. This data type can represent a number as large as 231, or in terms of bytes, roughly 2 GB. This is the maximum file length that can be represented in the datalogger directory table. Q: Why does a large card cause long program compile times? A: Program compile times increase with card and file sizes. As the datalogger boots up, the card must be searched to determine space available for data storage. In addition, for tables that are created by TableFile() with Option 64, an empty file that is large enough to hold all of the specified records must be created (i.e., 208

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Section 7.
Installation
Public
Sensor(10)
DataTable
(Ts_data,TRUE,-1)
'TableFile("filename",Option,MaxFiles,NumRec/TimeIntoInterval,Interval,Units,
'
OutStat,LastFileName)
TableFile
("CRD:"&Status.SerialNumber(1,1)&".ts_data_",64,-1,0,1,Day,0,0)
Sample
(10,sensor(1),IEEE4)
EndTable
BeginProg
Scan
(100,mSec,100,0)
'Measurement instructions go here.
'Processing instructions go here.
CallTable
ts_data
NextScan
EndProg
7.9.11.4 TableFile() with Option 64 Q & A
Q:
How does
Option 64
differ from other
TableFile()
options?
A:
Pre-allocation of memory combines with TOB3 data format to give
Option 64
two principal advantages over other
TableFile()
options.
These are:
increased runtime write performance
short card eject times
Option 64
is unique among table file options in that it pre-allocates enough
memory on the memory card to store an interval amount of data
1
.
Pre-allocation
allows data to be continuously and more quickly written to the card in ≈1 KB
blocks.
TOB3 binary format copies data directly from CPU memory to the
memory card without format conversion, lending additional speed and efficiency
to the data storage process.
Note
Pre-allocation of memory card files significantly increases run time write
performance.
It also reduces the risk of file corruption that can occur as a result
of power loss or incorrect card removal.
Note
To avoid data corruption and loss, memory card removal must always be
initiated by pressing the
Eject
button on the face of the CR6.
The card must be
ejected only after the
Act
light shows a solid green.
Q:
Why are individual files limited to 2 GB?
A:
In common with many other systems, the datalogger natively supports signed
four-byte integers.
This data type can represent a number as large as 231, or in
terms of bytes, roughly 2 GB.
This is the maximum file length that can be
represented in the datalogger directory table.
Q:
Why does a large card cause long program compile times?
A:
Program compile times increase with card and file sizes.
As the datalogger
boots up, the card must be searched to determine space available for data storage.
In addition, for tables that are created by
TableFile()
with
Option 64
, an empty file
that is large enough to hold all of the specified records must be created (i.e.,
208