VHDL Programming

Configurations 195

The information in this section on generics can be summarized by the

charts shown in Figures 7-3 and 7-4. (These charts were originally created

by Paul Krol.)

These charts shows the effect of the declarations and mapping of

generics on the values actually obtained in the model. The first four

columns of Figure 7-3 describe where a particular generic, G, can be

declared and mapped to a value. The next column describes the

error/warning number returned from a particular combination of decla-

ration and mapping. The next two columns describe the values obtained

by the generic, G, and any other generics for the entity for a particular

declaration and mapping combination. At the bottom of Figure 7-3 and in

Figure 7-4, are the tables of translations used to translate the character

values used to the appropriate action taken.

Board-Socket-Chip Analogy

A good analogy for describing how entity declarations, architectures, com-

ponent declarations, and configuration specifications all interact is the

Declaration Mapping Error / Generic Values

Warning

Entity Component Instance Configuration Same Other

DD A I E

DN A I E

DN A C E

ND A I M

ND A CM

X D / N A

X D / N

X D / N A

D / N X A

D / N X A C E

AA

XX

1 2 2 3 4 5

Figure 7-3
Configuration
Generic Table.