174 lines
5.2 KiB
Verilog
174 lines
5.2 KiB
Verilog
/*
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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 "defines.v"
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// core local interruptor module
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// 核心中断管理、仲裁模块
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module clint(
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input wire clk,
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input wire rst,
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// from id
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input wire[`INT_BUS] int_flag_i,
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input wire[`InstBus] inst_i,
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input wire[`InstAddrBus] inst_addr_i,
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// from ctrl
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input wire[`Hold_Flag_Bus] hold_flag_i,
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// from csr_reg
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input wire[`RegBus] data_i,
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// to csr_reg
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output reg we_o,
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output reg[`MemAddrBus] waddr_o,
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output reg[`MemAddrBus] raddr_o,
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output reg[`RegBus] data_o,
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// to ex
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output reg[`InstAddrBus] int_addr_o,
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output reg int_assert_o
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);
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// 状态定义
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localparam STATE_IDLE = 4'b0001;
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localparam STATE_ASSERT = 4'b0010;
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localparam STATE_WAIT_MRET = 4'b0100;
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localparam STATE_MRET = 4'b1000;
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reg[3:0] state;
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reg[3:0] next_state;
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// 状态更新
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always @ (posedge clk) begin
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if (rst == `RstEnable) begin
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state <= STATE_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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// 状态切换
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always @ (*) begin
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if (rst == `RstEnable) begin
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next_state <= STATE_IDLE;
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end else begin
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case (state)
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STATE_IDLE: begin
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// 目前只要外设有中断信号发出就立马响应.
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// 后续增加中断优先级(嵌套)时需要修改这里的逻辑
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if (int_flag_i != `INT_NONE) begin
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next_state <= STATE_ASSERT;
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end else begin
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next_state <= STATE_IDLE;
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end
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end
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STATE_ASSERT: begin
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next_state <= STATE_WAIT_MRET;
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end
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STATE_WAIT_MRET: begin
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if (inst_i == `INST_MRET) begin
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next_state <= STATE_MRET;
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end else begin
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next_state <= STATE_WAIT_MRET;
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end
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end
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STATE_MRET: begin
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next_state <= STATE_IDLE;
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end
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default: begin
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next_state <= STATE_IDLE;
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end
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endcase
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end
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end
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// 根据不同的状态,读取对应的CSR寄存器
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always @ (*) begin
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if (rst == `RstEnable) begin
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raddr_o <= `ZeroWord;
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end else begin
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case (state)
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STATE_IDLE: begin
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raddr_o <= {20'h0, `CSR_MTVEC};
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end
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STATE_ASSERT: begin
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raddr_o <= {20'h0, `CSR_MTVEC};
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end
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STATE_WAIT_MRET: begin
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raddr_o <= {20'h0, `CSR_MEPC};
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end
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STATE_MRET: begin
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raddr_o <= {20'h0, `CSR_MEPC};
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end
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default: begin
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raddr_o <= {20'h0, `CSR_MTVEC};
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end
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endcase
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end
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end
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// 发出中断信号
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// 中断响应和中断返回时都要发
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always @ (posedge clk) begin
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if (rst == `RstEnable) begin
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int_assert_o <= `INT_DEASSERT;
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int_addr_o <= `ZeroWord;
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end else begin
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case (state)
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STATE_ASSERT: begin
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int_assert_o <= `INT_ASSERT;
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int_addr_o <= data_i;
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end
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STATE_MRET: begin
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int_assert_o <= `INT_ASSERT;
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int_addr_o <= data_i;
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end
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default: begin
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int_assert_o <= `INT_DEASSERT;
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int_addr_o <= `ZeroWord;
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end
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endcase
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end
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end
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// 根据不同的状态,写对应的CSR寄存器
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always @ (posedge clk) begin
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if (rst == `RstEnable) begin
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we_o <= `WriteDisable;
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waddr_o <= `ZeroWord;
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data_o <= `ZeroWord;
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end else begin
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if (state == STATE_ASSERT) begin
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we_o <= `WriteEnable;
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waddr_o <= {20'h0, `CSR_MEPC};
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data_o <= inst_addr_i;
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end else begin
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we_o <= `WriteEnable;
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waddr_o <= {20'h0, `CSR_MCAUSE};
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data_o <= {24'h0, int_flag_i};
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end
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end
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end
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endmodule
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