waittest.v.txt

来自「基于Samsung2410平台的PCMCIA中的DMA测试程序和Wait程序」· 文本 代码 · 共 82 行

module WAITTEST(clock,nReset,nWAIT,data,nGCS,nOE);
    input clock,nReset;
    input nGCS,nOE;
    output nWAIT;
    output [3:0] data;

    reg nWAIT;
    reg preset;
    reg enCounter;
    reg [3:0] data;
    reg [2:0] wState;
    reg [3:0] counter;

    parameter [1:0] W0=0,W1=1,W2=2,W3=3,W4=4,W5=5,W6=6;
	
    always @(posedge clock or negedge nReset) 
	begin 
	    if(!nReset)counter=0;
	    else if(enCounter)counter=counter-1;
	    else if(preset)counter=0;
	end

    always @(posedge clock or negedge nReset)
	begin
	    if(!nReset)
		wState=W0;
	    else
		case(wState)
		    W0: if(nGCS)
			    wState=W0;
			else 
			    wState=W1;
		    W1: wState=W2;
		    W2: wState=W3;
		    W3:	if(counter>0)
		    	    wState=W3;
			else
			    wState=W4;
		    W4: wState=W5;
		    W5: if(nOE==0)
			    wState=W5;
			else 
			    if(nGCS==0)
				wState=W6;
			    else
				wState=W0;
		    W6: if(nGCS==0)
			    wState=W6;
			else
			    wState=W0;
		endcase
	end

    always @(wState)
	begin
	    preset=0; 
	    enCounter=0;
	    nWAIT=1;
	    data=4'b0101;
	    case(wState)
		W1: begin
			preset=1;
			nWAIT=0;
		    end
		W2: begin
			enCounter=1;
			nWAIT=0;
		    end
		W3: begin
			nWAIT=0;
			enCounter=1;
		    end
		W4: begin
			nWAIT=1;
			data=4'b1010;
		    end
		W5: data=4'b1010;
	    endcase
	end

endmodule