Altera Hardware Description Language

Altera Hardware Description Language (AHDL) is a proprietary hardware description language (HDL) developed by Altera Corporation. AHDL is used for digital logic design entry for Altera's complex programmable logic devices (CPLDs) and field-programmable gate arrays (FPGAs). It is supported by Altera's MAX-PLUS and Quartus series of design software. AHDL has an Ada-like syntax and its feature set is comparable to the synthesizable portions of the Verilog and VHDL hardware description languages. In contrast to HDLs such as Verilog and VHDL, AHDL is a design-entry language only; all of its language constructs are synthesizable. By default, Altera software expects AHDL source files to have a .tdf extension (Text Design Files).

Example

% a simple AHDL up counter, released to public domain 13 November 2006 %
% [block quotations achieved with percent sign] %
% like c, ahdl functions must be prototyped %

% PROTOTYPE:
 FUNCTION COUNTER (CLK)
	RETURNS (CNTOUT[7..0]); %

% function declaration, where inputs, outputs, and
bidirectional pins are declared %
% also like c, square brackets indicate an array %

SUBDESIGN COUNTER
(
	CLK		:INPUT;
	CNTOUT[7..0]	:OUTPUT;
)

% variables can be anything from flip-flops (as in this case),
tri-state buffers, state machines, to user defined functions %

VARIABLE
	TIMER[7..0]: DFF;

% as with all hardware description languages, think of this
 less as an algorithm and more as wiring nodes together %

BEGIN
	DEFAULTS

		TIMER[].prn = VCC; %  this takes care of d-ff resets %
		TIMER[].clrn = VCC;
	END DEFAULTS;

	TIMER[].d = TIMER[].q + H"1";
END;

gollark: I don't think any of us live close enough for avian carriers.

gollark: Actually, that seems like it would be hard and require much specialised knowledge.

gollark: I wonder if we can somehow exploit this to run APIONET at a lower level.

gollark: Oh, and fun things like the towers knowing your location fairly accurately at all times and "silent SMSes" and such.

gollark: Anyway, the phone network is a hellhole of poorly designed custom encryption, SIM cards which shouldn't exist and definitely shouldn't run Java but do (and have way too much possibly insecure onboard functionality), seemingly nonpublic standards, and modems with apioformic proprietary code doing ???.

References

Scarpino, Frank A., VHDL and AHDL Digital System Implementation. Prentice Hall PTR, 1998.

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