| `timescale 1 ns / 1 ps |
| |
| module top ( |
| input clk, |
| output reg LED0, LED1, LED2, LED3, LED4, LED5, LED6, LED7 |
| ); |
| // ------------------------------- |
| // Reset Generator |
| |
| reg [7:0] resetn_counter = 0; |
| wire resetn = &resetn_counter; |
| |
| always @(posedge clk) begin |
| if (!resetn) |
| resetn_counter <= resetn_counter + 1; |
| end |
| |
| |
| // ------------------------------- |
| // PicoRV32 Core |
| |
| wire mem_valid; |
| wire [31:0] mem_addr; |
| wire [31:0] mem_wdata; |
| wire [3:0] mem_wstrb; |
| |
| reg mem_ready; |
| reg [31:0] mem_rdata; |
| |
| picorv32 #( |
| .ENABLE_COUNTERS(0), |
| .LATCHED_MEM_RDATA(1), |
| .TWO_STAGE_SHIFT(0), |
| .TWO_CYCLE_ALU(1), |
| .CATCH_MISALIGN(0), |
| .CATCH_ILLINSN(0) |
| ) cpu ( |
| .clk (clk ), |
| .resetn (resetn ), |
| .mem_valid(mem_valid), |
| .mem_ready(mem_ready), |
| .mem_addr (mem_addr ), |
| .mem_wdata(mem_wdata), |
| .mem_wstrb(mem_wstrb), |
| .mem_rdata(mem_rdata) |
| ); |
| |
| |
| // ------------------------------- |
| // Memory/IO Interface |
| |
| // 128 32bit words = 512 bytes memory |
| localparam MEM_SIZE = 128; |
| reg [31:0] memory [0:MEM_SIZE-1]; |
| initial $readmemh("firmware.hex", memory); |
| |
| always @(posedge clk) begin |
| mem_ready <= 0; |
| if (resetn && mem_valid && !mem_ready) begin |
| (* parallel_case *) |
| case (1) |
| !mem_wstrb && (mem_addr >> 2) < MEM_SIZE: begin |
| mem_rdata <= memory[mem_addr >> 2]; |
| mem_ready <= 1; |
| end |
| |mem_wstrb && (mem_addr >> 2) < MEM_SIZE: begin |
| if (mem_wstrb[0]) memory[mem_addr >> 2][ 7: 0] <= mem_wdata[ 7: 0]; |
| if (mem_wstrb[1]) memory[mem_addr >> 2][15: 8] <= mem_wdata[15: 8]; |
| if (mem_wstrb[2]) memory[mem_addr >> 2][23:16] <= mem_wdata[23:16]; |
| if (mem_wstrb[3]) memory[mem_addr >> 2][31:24] <= mem_wdata[31:24]; |
| mem_ready <= 1; |
| end |
| |mem_wstrb && mem_addr == 32'h1000_0000: begin |
| {LED7, LED6, LED5, LED4, LED3, LED2, LED1, LED0} <= mem_wdata; |
| mem_ready <= 1; |
| end |
| endcase |
| end |
| end |
| endmodule |