Download LabVIEW FPGA Module User Manual

Chapter 2
Creating FPGA VIs
The equation you use to convert a voltage to a binary representation
depends on the specific FPGA device. Refer to the hardware
documentation for more information. For example, with an NI PXI-7831R
device, use the following equation to convert the voltage to the binary
representation:
Voltage × 32768Binary Code = Output
------------------------------------------------------------10.0 V
Avoid executing this calculation in the FPGA VI because the FPGA only supports
integer operations. Also, performing the equation on the FPGA uses additional space on
the FPGA. Refer to the Mathematical Operations section for more information.
Note
Digital I/O
You can treat digital resources as individual lines or as predefined groups
of eight digital lines, also known as ports. A terminal is either an individual
digital line or a digital port depending on which FPGA Device I/O function
you use. You can perform both digital input and digital output on any
digital terminal. Refer to the LabVIEW Help, available by selecting
Help»VI, Function, & How-To Help, for information about specific
FPGA Device I/O functions and port assignments.
Use the Digital Input and Digital Port Input functions to read the state of a
digital terminal or digital port. The state of the digital terminal is commonly
determined by an external signal, such as the output generated by an
external device. Use the Digital Output and Digital Port Output functions
to set the state of a digital terminal or port. You can use the Digital Input
functions to verify the state of the same terminal to which the Digital
Output function writes.
If you have used a terminal for output, you must use the Digital Enable or Digital
Port Enable function to disable the terminal for output before the Digital Input function can
read the state of an external signal.
Note
The Digital Output and Digital Port Output functions both write the data
and enable the terminal for output. You also can use the Digital Data and
Digital Port Data functions, which write data to a terminal but do not enable
the output. Use the Digital Enable and Digital Port Enable functions to
enable the digital terminal, which allows the data to be driven out. For
example, you might have one portion of the block diagram continuously
generating an internal signal. Use a Digital Enable or Digital Port Enable
function in another portion of the block diagram to independently control
when the internal signal is actually driven out to an external device.
FPGA Module User Manual
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