HP VXI 75000 C Series, User'S And Scpi Programming Manual

Page: 88 / 438

88 Programming the HP E1415 for PID Control Chapter 3
NOTE
After *RST/Power-on, each element in the CVT contains the IEEE-754
value "Not-a Number" (NaN). Channel values which are a positive
overvoltage return IEEE +INF and negative overvoltage return IEEE -INF.
Refer to the FORMat command in on page 206 for the NaN, +INF, and -INF
values for each data format.
The command used to return values from CVT elements is the
[SENSe:]DATA:CVT?
(@<element_list>). <element_list> has the same
form as a <ch_list> parameter. The format of returned data is dependent on
the current setting from the FORMat command.
To access the latest values from PIDB algorithms ALG1:
SENS:DATA:CVT? (@10:13)
returns Sense, Error, Output,
and Status values from ALG1
execute program input statement here
must input 4 values
To return the latest values from PIDB Alg1 and PIDB ALG2:
SENS:DATA:CVT? (@10:13,20:23)
returns Sense, Error, Output,
and Status values from ALGs 1
and 2
execute program input statement here
must input 8 values
To reset the CVT > (and set all values to NaN), send the command
[SENSe:]DATA:CVTable:RESet.
Reading History
Mode Values From
the FIFO
The algorithm history mode enables PIDB algorithms to send their operating
values to the FIFO buffer. To enable the PIDB algorithm to send its
operating values to the FIFO, set the History_mode variable to 1. If you need
to retrieve the value of the working variables from every execution of your
algorithm, the FIFO is the best choice. Since it is a buffer that can store up
to 65,024 values, your application program can read the FIFO values
intermittently and still keep up with the data rate from the algorithm. The
commands provided for reading the FIFO are:
FIFO Transfer Commands
[SENSe:]DATA:FIFO[:ALL]? returns all values remaining in the FIFO.
This command should be used only when no more values are being placed
in the FIFO (algorithms stopped).
[SENSe:]DATA:FIFO:HALF? returns 32,768 values (approximately half of
the FIFO capacity) when they become available. This command completes
only after the 32,768 values are transferred.
[SENSe:]DATA:FIFO:PART? <n_values> returns the number of values
specified by <n_values> (2,147,483,647 maximum). This command
completes only after n_values have been transferred.