NIOS II 自定义IP核编写基本框架
关于自定义IP 1、接口 a、全局信号 时钟(Clk),复位(reset_n) b、avalon mm slave 地址(as_address) 片选(as_chipselect /as_chipselect_n) 写请求(as_write / as_write_n) 写数据(as_writedata(按照字节对齐,8/16/32位位宽) 读请求(as_read / as_read_n) 读数据(as_readdata)(按照字节对齐,8/16/32位位宽) 等待信号(as_waitrequest / as_waitrequest_n) 读数据有效信号(as_data_valid) 中断请求(irq / irq_n) c、导出信号,导出到NIOS 系统顶层,分配到IO,或者连接到Qsys系统以外的逻辑 2、内部寄存器和线网的定义 数据寄存器(读/写) 状态寄存器(IP运行状态、数据状态……) 控制寄存器 中断屏蔽寄存器 用户自定义寄存器 3、Avalon总线对寄存器的读写 //写入数据 always@(posedge clk or negedge reset_n) if(!reset_n) channel <= 3\'d0; else if(as_chipselect && as_write && (as_address == 1)) channel <= as_writedata[2:0]; //写指定地址实现相应功能,不考虑写入值 always@(posedge clk or negedge reset_n) if(!reset_n) control <= 1\'d0; else if(as_chipselect && as_write && (as_address == 3)) control <= 1\'d1; else control <= 1\'d0; //读寄存器逻辑 always@(posedge clk or negedge reset_n) if(!reset_n) as_readdata <= 16\'d0; else if(as_chipselect && as_read)begin case(as_address) 0:as_readdata <= {4\'d0, data}; 1:as_readdata <= {13\'d0, channel}; 2:as_readdata <= {8\'d0, freq_sclk}; 4:as_readdata <= {15\'d0, irqmask}; 5:as_readdata <= {14\'d0, status}; default:as_readdata <= 16\'d0; endcase end 4、用户逻辑对寄存器的赋值 always@(posedge clk or negedge reset_n) if(!reset_n) status[0] <= 1\'d0; else if(Conv_Done) status[0] <= 1\'b1; else if(as_chipselect && as_read && (as_address == 0)) status[0] <= 1\'b0; always@(posedge clk or negedge reset_n) if(!reset_n) status[1] <= 1\'d0; else if(ADC_State) status[1] <= 1\'b1; else status[1] <= 1\'b0;