Digital Signal Processing Reference
In-Depth Information
Figure 1.28
Floorplan view showing the internal FPGA I/O and LE placements of an OR-gate on a
DE1. User logic and pins used in the design are seen as shaded areas in the lower right corner.
1.15 Symbols and Hierarchy
The Symbol Editor is used to edit or create a symbol to represent a logic
circuit. Symbols can be created for a design whenever a VHDL or Verilog file
is compiled. Create a symbol for your VHDL design by opening the orgate.vhd
file, and then select
File
Create/Update
Create Symbol Files for
Current File.
Select
File
Open,
change the file type setting for *.bsf, find and chose
orgate.bsf
to see the new symbol for your VHDL based design as shown in
Figure 1.29. Inputs are typically shown on the left side of the symbol and
outputs on the right side. Symbols are used for design hierarchy in more
complex schematics. This new symbol can be used to add the circuit to a
design with the graphic editor just like the BNOR2 symbol that was used
earlier in the tutorial. Double clicking on a symbol in the graphic editor will
open a pop-up requesting, “Select one design file.” Selecting the appropriate
*.vhd, *.v, or *.bdf, file takes the user to the underlying Verilog, VHDL, or
graphic file respectively by opening the underlying file in a different screen
tab.
