VTI Instruments EX1000A, User Manual

Page: 68 / 320

VTI Instruments Corp.
68 EX10xxA Triggering
The amount of scans that can be buffered within the memory is dependent on the number of channels
in the scan list and the requested data format. For this reason, very long scan sequences (in terms of
count) will benefit from a minimization of the data format, so as to maximize the number of scans
that can be stored. Specifically, the number of scans that can be buffered (Page_Count) is determined
by the following formula:
Reporting Timestamp_ 2 4 ze Channel_Si
  
Reporting Timestamp_ 2 4 l_Size CJC_Channe
  
ing CJC_Report 2 1 l_Count CJC_Channe
 
l_Size CJC_Channe l_Count CJC_Channe ze Channel_Si unt Channel_Co 2 9 Page_Size
    
Page_Size / 14680064 Page_Count

where: Channel_Count
1-48 (number of channels in scan list)
CJC_Reporting 0 or 1 (1 = YES, 0 = NO)
Timestamp_Reporting 0 or 1 (1 = YES, 0 = NO)
Page_Count sizes for some typical configurations are the following:
Channel_Count CJC_Reporting Timestamp_Reporting Page_Count
1 0 0 152916
16 0 0 94101
32 0 0 66726
48 0 0 51689
48 1 0 44216
48 0 1 38630
48 1 1 32477
T
ABLE
3-11: E
XAMPLE
P
AGE
C
OUNT
S
IZES
If the reading buffer fills to its maximum capacity during scanning, the behavior with regards to
additional readings is governed by the setting of the instrument’s blocking mode. With blocking
mode enabled, additional readings are discarded, leaving the contents of the buffer intact. With
blocking mode disabled, the buffer becomes circular, in that additional readings overwrite the oldest
readings.
The default selection for blocking mode is disabled.
NOTE The reading buffer memory is volatile and is cleared upon an instrument reset or power cycle.
R
ETRIEVING
D
ATA
In general, acquisition data is retrieved from the EX10xxA upon the completion of the acquisition.
This mode of operation is fully supported by the embedded web page as well as the instrument
driver. In addition, data retrieval in the midst of an acquisition sequence is supported by the
instrument driver. In either case, retrieved data is fully calibrated and compensated by the EX10xxA
and output directly in the requested units. No post-acquisition user manipulations are required. Data
can be retrieved one page (scan) at a time or downloaded in multiple page blocks up to the maximum
number of pages that exist on the instrument at the time of retrieval. In order to provide the
maximum reading buffer capacity for future acquisitions, data is deleted from the FIFO memory
upon retrieval.
Applications may retrieve data from this FIFO using either the Read FIFO or Streaming Data
interfaces. Please refer to the
Retrieving Data (Read FIFO and Streaming Data) section for further
details. Once data is retrieved from the FIFO, via either method, it is no longer kept within the FIFO.