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About Fast Data Channel (FDC) Operation
2–18
VX4101A MultiPaq Instrument User Manual
You must establish the I/O linkage between the host and the VX4101A DAC.
You use both Word Serial Protocol (WSP) and FDC I/O drivers. Two commu-
nications sessions will be required: one for WSP and one for FDC.
Command Syntax. You use the following command syntax:
viOpen (session, resource name, access mode, timeout, vi);
Example Code. You can use the following code to open and close the FDC
session:
errs = viOpen (visaRM, VX4101Desc, VI_NULL,VI_NULL, &fdc);
errs = viOpen (visaRM, VX4101Desc, VI_NULL, VI_NULL , &wsp);
Successful execution of these commands returns the associated I/O driver
reference handle in the parameter pointed to by wsp or fdc.
In this section, you will prepare the FDC channel to transmit data.
Before You Begin. Before the channel can be configured, the host needs to know
which physical FDC channels are supported by the instrument. You can retrieve
this information from the instrument by issuing the following query:
VXI:FDC?
This query returns a comma separated list of integers that represent the numeric
values of the physical FDC channels supported by the instrument.
Command Syntax. This is an ASCII command and is sent through the WSP
channel using the VISA functions, viRead and viWrite. Use the following the
syntax to program FDC to read and write data:
viRead (session, buff, max count, return count);
viWrite (session, buff, length(buff), return count);
Example Code for Configuring the FDC Channel. You can use the following code
to prepare the FDC channel to transmit data:
errs = viWrite (wsp, "VXI:FDC?", 8, &RetCnt);
errs = viRead (wsp, buff, sizeof(buff), &RetCnt);
fdc_physical_channel = atoi(buff);
Establishing a
Communications Session
Configuring the FDC
Channel