129 lines
4.0 KiB
Systemverilog
129 lines
4.0 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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// 数据接收端模块
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// 跨时钟域传输，全(四次)握手协议
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// req = 1
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// ack_o = 1
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// req = 0
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// ack_o = 0
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module full_handshake_rx #(
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parameter DW = 32)( // RX要接收数据的位宽
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input wire clk, // RX端时钟信号
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input wire rst_n, // RX端复位信号
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// from tx
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input wire req_i, // TX端请求信号
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input wire[DW-1:0] req_data_i, // TX端输入数据
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// to tx
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output wire ack_o, // RX端应答TX端信号
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// to rx
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output wire[DW-1:0] recv_data_o,// RX端接收到的数据
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output wire recv_rdy_o // RX端是否接收到数据信号
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);
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localparam STATE_IDLE = 2'b01;
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localparam STATE_DEASSERT = 2'b10;
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reg[1:0] state;
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reg[1:0] state_next;
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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 <= STATE_IDLE;
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end else begin
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state <= state_next;
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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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// 等待TX请求信号req=1
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STATE_IDLE: begin
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if (req == 1'b1) begin
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state_next = STATE_DEASSERT;
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end else begin
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state_next = STATE_IDLE;
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end
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end
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// 等待req=0
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STATE_DEASSERT: begin
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if (req) begin
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state_next = STATE_DEASSERT;
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end else begin
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state_next = STATE_IDLE;
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end
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end
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default: begin
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state_next = STATE_IDLE;
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end
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endcase
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end
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reg req_d;
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reg req;
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// 将请求信号打两拍进行同步
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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req_d <= 1'b0;
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req <= 1'b0;
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end else begin
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req_d <= req_i;
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req <= req_d;
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end
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end
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reg[DW-1:0] recv_data;
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reg recv_rdy;
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reg ack;
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always @ (posedge clk or negedge rst_n) begin
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if (!rst_n) begin
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ack <= 1'b0;
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recv_rdy <= 1'b0;
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recv_data <= {(DW){1'b0}};
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end else begin
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case (state)
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STATE_IDLE: begin
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if (req == 1'b1) begin
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ack <= 1'b1;
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recv_rdy <= 1'b1; // 这个信号只会持续一个时钟
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recv_data <= req_data_i; // 这个信号只会持续一个时钟
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end
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end
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STATE_DEASSERT: begin
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recv_rdy <= 1'b0;
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recv_data <= {(DW){1'b0}};
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// req撤销后ack也撤销
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if (req == 1'b0) begin
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ack <= 1'b0;
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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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assign ack_o = ack;
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assign recv_rdy_o = recv_rdy;
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assign recv_data_o = recv_data;
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endmodule
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