VXI VT1422A - Manual (Page 165)

Advanced Programming with the VT1529B 163 Chapter 5
Because the EU conversions for temperature and strain are performed in the
host computer, not by the on-board DSP, a fast computer may be needed in
order to keep up with multiple VT1529B’s scanning at full speed. These
conversions use the full strain and ITS-90 thermocouple conversion
equations, which offers more accuracy than the on-board DSP approximations,
but at the cost of being slower to compute. A PC with a Pentium
®
III
800 MHz processor or faster is recommended.
Note
Channels programmed using the old commands are unaffected by these
changes. The on-board DSP will perform the engineering units conversion.
Only channels programmed using the new commands are affected.
Note
Channels programmed with the old and new commands on a VT1529B can
be intermixed.
Must Count
writefifo Calls in
Algorithms
Because the VXIplug&play driver does the engineering units conversion for
all channels programmed with the new commands, the driver needs to
understand the order of data in the FIFO, matching the FIFO data with the
appropriate channel’s EU. This means that the driver must be made aware of
any extra data written to the FIFO by any algorithms that has been
downloaded. All writefifo() calls need to be counted in an algorithm and this
count should be provided to the driver so that proper synchronization
between the FIFO data and the scan list is maintained. This count is the third
parameter to the hpe1422_readFifoPost_Q() driver call.
New SCPI
Commands
In the VXIplug&play driver, there are some new calls. There are also new
SCPI commands that support the new functionality of the VT1529B. Some
of these commands are completely new while other commands are similar
to the existing SCPI commands except that they have the :POST keyword
and/or an extra parameter added to them. The new SCPI commands are
used with the “pass-through” functions in the VXIplug&play driver.
For complete information on the new SCPI commands, see the Command
Reference Section (Chapter 7).
Note
See the VT1422A VXIplug&play driver’s help file for details on the
“pass-through” functions.