426 lines
13 KiB
Systemverilog
426 lines
13 KiB
Systemverilog
/*
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Copyright 2020 Blue Liang, liangkangnan@163.com
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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`include "../core/defines.sv"
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// 串口收发模块(默认: 115200, 8，N，1)
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module uart(
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input wire clk,
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input wire rst_n,
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input wire[31:0] addr_i,
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input wire[31:0] data_i,
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input wire[3:0] sel_i,
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input wire we_i,
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output wire[31:0] data_o,
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output wire tx_pin,
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input wire rx_pin
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);
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// 波特率115200bps
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localparam BAUD_115200 = `CPU_CLOCK_HZ / 115200;
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localparam S_IDLE = 4'b0001;
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localparam S_START = 4'b0010;
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localparam S_SEND_BYTE = 4'b0100;
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localparam S_STOP = 4'b1000;
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reg[3:0] state;
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reg[3:0] next_state;
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reg[15:0] cycle_cnt;
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reg tx_bit;
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reg[3:0] bit_cnt;
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reg rx_q0;
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reg rx_q1;
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wire rx_negedge;
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reg rx_start; // RX使能
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reg[3:0] rx_clk_edge_cnt; // clk沿的个数
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reg rx_clk_edge_level; // clk沿电平
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reg rx_done;
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reg[15:0] rx_clk_cnt;
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reg[15:0] rx_div_cnt;
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reg[7:0] rx_data;
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reg rx_over;
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// 寄存器(偏移)地址
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localparam UART_CTRL = 8'h0;
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localparam UART_STATUS = 8'h4;
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localparam UART_BAUD = 8'h8;
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localparam UART_TXDATA = 8'hc;
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localparam UART_RXDATA = 8'h10;
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// UART控制寄存器，可读可写
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// bit[0]: UART TX使能, 1: enable, 0: disable
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// bit[1]: UART RX使能, 1: enable, 0: disable
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reg[31:0] uart_ctrl;
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// UART状态寄存器
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// 只读，bit[0]: TX空闲状态标志, 1: busy, 0: idle
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// 可读可写，bit[1]: RX接收完成标志, 1: over, 0: receiving
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reg[31:0] uart_status;
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// UART波特率寄存器(分频系数)，可读可写
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reg[31:0] uart_baud;
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// UART发送数据寄存器，可读可写
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reg[31:0] uart_tx;
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// UART接收数据寄存器，只读
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reg[31:0] uart_rx;
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wire wen = we_i;
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wire ren = (~we_i);
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wire write_reg_ctrl_en = wen & (addr_i[7:0] == UART_CTRL);
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wire write_reg_status_en = wen & (addr_i[7:0] == UART_STATUS);
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wire write_reg_baud_en = wen & (addr_i[7:0] == UART_BAUD);
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wire write_reg_txdata_en = wen & (addr_i[7:0] == UART_TXDATA);
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wire tx_start = write_reg_txdata_en & sel_i[0] & uart_ctrl[0] & (~uart_status[0]);
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wire rx_recv_over = uart_ctrl[1] & rx_over;
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assign tx_pin = tx_bit;
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// 写uart_rxdata
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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uart_rx <= 32'h0;
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end else begin
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// 接收完成时，保存接收到的数据
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if (rx_recv_over) begin
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uart_rx[7:0] <= rx_data;
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end
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end
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end
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// 写uart_txdata
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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uart_tx <= 32'h0;
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end else begin
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// 开始发送时，保存要发送的数据
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if (tx_start) begin
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uart_tx[7:0] <= data_i[7:0];
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end
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end
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end
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// 写uart_status
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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uart_status <= 32'h0;
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end else begin
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if (write_reg_status_en & sel_i[0]) begin
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// 写RX完成标志
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uart_status[1] <= data_i[1];
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end else begin
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// 开始发送数据时，置位TX忙标志
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if (tx_start) begin
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uart_status[0] <= 1'b1;
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// 发送完成时，清TX忙标志
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end else if ((state == S_STOP) & (cycle_cnt == uart_baud[15:0])) begin
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uart_status[0] <= 1'b0;
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// 接收完成，置位接收完成标志
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end
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if (rx_recv_over) begin
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uart_status[1] <= 1'b1;
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end
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end
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end
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end
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// 写uart_ctrl
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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uart_ctrl <= 32'h0;
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end else begin
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if (write_reg_ctrl_en & sel_i[0]) begin
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uart_ctrl[7:0] <= data_i[7:0];
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end
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end
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end
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// 写uart_baud
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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uart_baud <= BAUD_115200;
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end else begin
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if (write_reg_baud_en) begin
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if (sel_i[0]) begin
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uart_baud[7:0] <= data_i[7:0];
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end
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if (sel_i[1]) begin
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uart_baud[15:8] <= data_i[15:8];
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end
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end
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end
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end
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reg[31:0] data_r;
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// 读寄存器
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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data_r <= 32'h0;
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end else begin
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if (ren) begin
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case (addr_i[7:0])
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UART_CTRL: data_r <= uart_ctrl;
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UART_STATUS: data_r <= uart_status;
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UART_BAUD: data_r <= uart_baud;
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UART_RXDATA: data_r <= uart_rx;
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default: data_r <= 32'h0;
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endcase
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end else begin
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data_r <= 32'h0;
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end
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end
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end
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assign data_o = data_r;
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// *************************** TX发送 ****************************
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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state <= S_IDLE;
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end else begin
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state <= next_state;
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end
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end
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always @ (*) begin
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case (state)
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S_IDLE: begin
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if (tx_start) begin
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next_state = S_START;
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end else begin
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next_state = S_IDLE;
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end
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end
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S_START: begin
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if (cycle_cnt == uart_baud[15:0]) begin
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next_state = S_SEND_BYTE;
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end else begin
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next_state = S_START;
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end
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end
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S_SEND_BYTE: begin
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if ((cycle_cnt == uart_baud[15:0]) & (bit_cnt == 4'd7)) begin
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next_state = S_STOP;
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end else begin
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next_state = S_SEND_BYTE;
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end
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end
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S_STOP: begin
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if (cycle_cnt == uart_baud[15:0]) begin
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next_state = S_IDLE;
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end else begin
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next_state = S_STOP;
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end
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end
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default: begin
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next_state = S_IDLE;
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end
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endcase
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end
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// cycle_cnt
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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cycle_cnt <= 16'h0;
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end else begin
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if (state == S_IDLE) begin
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cycle_cnt <= 16'h0;
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end else begin
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if (cycle_cnt == uart_baud[15:0]) begin
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cycle_cnt <= 16'h0;
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end else begin
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cycle_cnt <= cycle_cnt + 16'h1;
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end
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end
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end
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end
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// bit_cnt
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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bit_cnt <= 4'h0;
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end else begin
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case (state)
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S_IDLE: begin
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bit_cnt <= 4'h0;
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end
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S_SEND_BYTE: begin
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if (cycle_cnt == uart_baud[15:0]) begin
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bit_cnt <= bit_cnt + 4'h1;
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end
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end
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endcase
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end
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end
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// tx_bit
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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tx_bit <= 1'b0;
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end else begin
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case (state)
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S_IDLE, S_STOP: begin
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tx_bit <= 1'b1;
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end
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S_START: begin
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tx_bit <= 1'b0;
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end
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S_SEND_BYTE: begin
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tx_bit <= uart_tx[bit_cnt];
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end
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endcase
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end
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end
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// *************************** RX接收 ****************************
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_q0 <= 1'b0;
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rx_q1 <= 1'b0;
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end else begin
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rx_q0 <= rx_pin;
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rx_q1 <= rx_q0;
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end
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end
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// 下降沿检测(检测起始信号)
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assign rx_negedge = rx_q1 & (~rx_q0);
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// 产生开始接收数据信号，接收期间一直有效
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_start <= 1'b0;
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end else begin
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if (uart_ctrl[1]) begin
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if (rx_negedge) begin
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rx_start <= 1'b1;
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end else if (rx_clk_edge_cnt == 4'd9) begin
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rx_start <= 1'b0;
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end
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end else begin
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rx_start <= 1'b0;
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end
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end
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end
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_div_cnt <= 16'h0;
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end else begin
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// 第一个时钟沿只需波特率分频系数的一半
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if (rx_start == 1'b1 && rx_clk_edge_cnt == 4'h0) begin
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rx_div_cnt <= {1'b0, uart_baud[15:1]};
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end else begin
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rx_div_cnt <= uart_baud[15:0];
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end
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end
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end
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// 对时钟进行计数
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_clk_cnt <= 16'h0;
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end else if (rx_start == 1'b1) begin
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// 计数达到分频值
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if (rx_clk_cnt == rx_div_cnt) begin
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rx_clk_cnt <= 16'h0;
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end else begin
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rx_clk_cnt <= rx_clk_cnt + 16'h1;
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end
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end else begin
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rx_clk_cnt <= 16'h0;
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end
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end
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// 每当时钟计数达到分频值时产生一个上升沿脉冲
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_clk_edge_cnt <= 4'h0;
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rx_clk_edge_level <= 1'b0;
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end else if (rx_start == 1'b1) begin
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// 计数达到分频值
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if (rx_clk_cnt == rx_div_cnt) begin
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// 时钟沿个数达到最大值
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if (rx_clk_edge_cnt == 4'd9) begin
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rx_clk_edge_cnt <= 4'h0;
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rx_clk_edge_level <= 1'b0;
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end else begin
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// 时钟沿个数加1
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rx_clk_edge_cnt <= rx_clk_edge_cnt + 4'h1;
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// 产生上升沿脉冲
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rx_clk_edge_level <= 1'b1;
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end
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end else begin
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rx_clk_edge_level <= 1'b0;
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end
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end else begin
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rx_clk_edge_cnt <= 4'h0;
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rx_clk_edge_level <= 1'b0;
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end
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end
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// bit序列
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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rx_data <= 8'h0;
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rx_over <= 1'b0;
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end else begin
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if (rx_start == 1'b1) begin
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// 上升沿
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if (rx_clk_edge_level == 1'b1) begin
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case (rx_clk_edge_cnt)
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// 起始位
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1: begin
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end
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// 第1位数据位
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2: begin
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if (rx_pin) begin
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rx_data <= 8'h80;
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end else begin
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rx_data <= 8'h0;
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end
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end
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// 剩余数据位
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3, 4, 5, 6, 7, 8, 9: begin
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rx_data <= {rx_pin, rx_data[7:1]};
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// 最后一位接收完成，置位接收完成标志
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if (rx_clk_edge_cnt == 4'h9) begin
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rx_over <= 1'b1;
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end
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end
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endcase
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end
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end else begin
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rx_data <= 8'h0;
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rx_over <= 1'b0;
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end
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end
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end
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endmodule
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