VHDL Programming

Data Types 103

WRITE(file, data)Procedure

ENDFILE(file)Function, returns boolean

Procedure READreads an object from the file and returns the object in

argument data. Procedure WRITEwrites argument data to the file specified

by the file argument. Finally, function ENDFILEreturns true when the file

is currently at the end-of-file mark.

Using these procedures and functions requires a file type declaration

and a file object declaration.

FILE TYPE DECLARATION A file type declaration specifies the

name of the file type and the base type of the file. Following is an example

of a file type declaration:

TYPE integer_file IS FILE OF INTEGER;

This declaration specifies a file type whose name is integer_fileand

is of type INTEGER. This declaration corresponds to the file in Figure 4-10.

FILE OBJECT DECLARATION A file object makes use of a file type

and declares an object of type FILE. The file object declaration specifies

the name of the file object, the mode of the file, and the physical disk path

name. The file mode can be INor OUT. If the mode is IN, then the file can

be read with the READprocedure. If the mode is OUT, then the file can be

written with the WRITEprocedure. Here is an example:

FILE myfile : integer_file IS IN

“/doug/test/examples/data_file”;

This declaration declares a file object called myfilethat is an input file

of type integer_file. The last argument is the path name on the physical

Figure 4-10 Integer 1 Integer 2 ............ Integer N End of File

Pictorial Representa-

tion of Integer File.

OPCODE

ADDRMODE

SRC

DST

OPCODE

ADDRMODE

SRC

DST

OPCODE

ADDRMODE

SRC

DST

...........

...........

...........

...........

END

OF

FILE

MARK

Figure 4-11

Pictorial Representa-

tion of Complex File.