Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Introduction Verilog is a HARDWARE DESCRIPTION LANGUAGE (HDL) A hardware description language is a language or means used to describe or model a digital system: a network switch, a microprocessor a memory or a simple flip-flop. It is design representation of digital hardware describes to design software. It is a C like programming language Hardware Description A digital circuit is defined as a module, like the function in C. module device_identifier ( I/O list ); declaration of I/O; declaration of internal wire connections; circuit description in either structural model or behavioral model endmodule module gate1 (x1, x2, f ); input x1, x2 ; output f ; nand g1 (f, x1, x2); assign f = ~ (x1 & x2); endmodule Structural Model / Gate Level Model Circuit described in structural model is to define the circuit composes of: What type of devices / logic gates How they are connected In gate level model, all common logic gates are supported. Specified by: gate_type identifier (output, inputs); not, and, nand, or, nor, xor Structural Model To use a predefined component, in Verilog, it is like functional call in C. what component is being called how it is connected to ( I/O lists, and its order ) Johnson Counter module johnson_counter ( clk, q0, q1, q2, q3 ) ; input clk ; output q0, q1, q2, q3 ; wire qb0, qb1, qb2, qb3 ; dff d0 ( clk , qb3 , q0 , qb0) ; dff d1 ( clk , q0 , q1 , qb1) ; dff d2 ( clk , q1 , q2 , qb2) ; dff d3 ( clk , q2 , q3 , qb3) ; endmodule /* D flip flop is a predefined component */ module dff (clk , D, Q, Qb); input clk, D; output Q, Qb; always @(posedge clk) Q <= D; Qb <= ~D; endmodule Behavioral Model Circuit described in behavioral model is to define the circuit by: the logic functionality Specified by: assign output = logic function (inputs); ~ : not & : and | : or