Design Entry Techniques
CPLD Schematic Design Guide
2-19
3.
In Viewdraw, open a symbol window and create a new symbol
named regxor as shown in the "The REGXOR Symbol" figure.
The symbol has three input pins and one output pin corre-
sponding to the pins defined in the ABEL equation file.
Figure 2-7
The REGXOR Symbol
4.
Make sure the symbol is defined as a primitive. For example, if
you are using WorkView Office, use the
Change
Symbol
Type
Module
command to indicate that there is no under-
lying schematic for the symbol. Then save the symbol in your
project directory.
5.
Instantiate the symbol in your schematic and connect its input
and output pins to logic and/or I/O buffers in your design.
6.
Select the regxor component in your schematic and add the
attribute
FILE=regxor
.
Hierarchical Design
You can create custom symbols with schematics under them and
place these symbols in your top-level or lower-level schematics to
create a hierarchical design. This can make your design more
modular and easier to understand.
Custom symbols with schematics under them are termed user macros,
as opposed to behavioral modules, which are custom symbols with
equations or HDL under them.
The procedure for creating a symbol with an underlying schematic is
the same for CPLD and FPGA families:
1.
Create a lower-level schematic using CPLD library symbols or
other custom symbols. To make a device-independent macro, use
X4864
REGXOR
CLK
I1
I0
Q
Summary :
In Viewdraw, open a symbol window and create a new symbol named regxor as shown in the "The REGXOR Symbol" figure. Hierarchical Design You can create custom symbols with schematics under them and place these symbols in your top-level or lower-level schematics to create a hierarchical design.
Tags :
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