key_arm_rd.v

本文件用于spi接口的键盘扫描模块

module key_arm_rd(clk,clr,key_value,key_flag,
				  addr,ncs,nwe,data,rd_enable);
	input       clk;
	input       clr;
	input[7:0]  key_value;
	input       key_flag;
	input[5:0]  addr;
	input       ncs;
	input       nwe;
	output[7:0] data;
	output      rd_enable;
	
	reg[7:0]    data;
	reg         rd_enable;
	reg         rd_en,rd_en1,rd_en2;
		
//ARM read key board value
	always @ (posedge clk or posedge clr)
		if(clr)
			data = 8'bz;
		else if((addr == 6'b000010) && !ncs && !nwe)
			data = key_value;
		else if((addr == 6'b000100) && !ncs && !nwe)
			data = {7'b0,key_flag};
		else
			data = 8'bz;
			
	always @ (posedge clk or posedge clr)
		if(clr)
			rd_en = 1'b0;
		else if((addr == 6'b000010) && !ncs && !nwe)
			rd_en = 1'b1;
		else
			rd_en = 1'b0;
			
	always @ (posedge clk or posedge clr)
		if(clr)
			begin
				rd_en1 <= 1'b1;
				rd_en2 <= 1'b1;
			end
		else 
			begin
				rd_en1 <= rd_en;
				rd_en2 <= rd_en1;
			end
	
	always @ (posedge clk or posedge clr)
		if(clr)
			rd_enable = 1'b0;
		else if(!rd_en2 && rd_en1)
			rd_enable = 1'b1;
		else
			rd_enable = 1'b0;
endmodule