VXI VT1422A - Manual (Page 136)

134 Programming the VT1422A for Data Acquisition and Control Chapter 4
Reading Running Algorithm Values
The most efficient means of acquiring algorithm derived data from the
VT1422A is to have its algorithms store real-number results in the FIFO or
CVT. The algorithms use the writefifo(), writecvt(), and writeboth()
intrinsic functions to perform this operation as shown below.
Reading CVT Data
Note that the first ten elements of the CVT are unavailable. These are used
by the driver for internal data retrieval. However, all algorithms have access
to the remaining 502 elements. Data is retrieved from the CVT with the
SCPI command DATA:CVT? (@10,12,14:67)
For VXIplug&play Users: Use the function hpe1422_readCVT_Q for
reading contiguous elements or hpe1422_cmdReal64Arr_Q(ViSession vi,
’DATA:CVT? (@<element_list>)’, ViInt32 size, ViReal64 _VI_FAR
result[ ], ViPInt32 count) for non-contiguous elements (as in the example
above). See the VT1422A plug&play driver Help file.
The format of data coming from the CVT is determined by the FORMat
command.
Important!
There is a fixed relationship between channel number and CVT element
for values from channels placed in the Scan List with ROUT:SEQ:DEF.
When mixing Scan List data acquisition with algorithm data storage, be
careful not to overwrite Scan List generated values with algorithm generated
values. See “ROUTe:SEQuence:DEFine” on page 323. for controlling CVT
entries from the analog scan list.
CVT 10
Note: CVT 0 - 9 unavailable
writecvt( <expr>, 10 );
writecvt( <expr>, 13 );
writeboth( <expr>, 14 );
writefifo( <expr> );
CVT 11
CVT 12
CVT 13
CVT 14
CVT 511
(65,024 elements)
Current Value Table (CVT)
(502 elements)
First-in-First-Out Data Buffer (FIFO)