Merge commit '3291d86ec38031e191ec1e7e5e8ddfa74b77cb7c' as 'picorv32'

1 files changed, 137 insertions, 0 deletions

diff --git a/picorv32/picosoc/simpleuart.v b/picorv32/picosoc/simpleuart.v
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+++ b/picorv32/picosoc/simpleuart.v
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+/*
+ *  PicoSoC - A simple example SoC using PicoRV32
+ *
+ *  Copyright (C) 2017  Claire Xenia Wolf <claire@yosyshq.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+module simpleuart #(parameter integer DEFAULT_DIV = 1) (
+	input clk,
+	input resetn,
+
+	output ser_tx,
+	input  ser_rx,
+
+	input   [3:0] reg_div_we,
+	input  [31:0] reg_div_di,
+	output [31:0] reg_div_do,
+
+	input         reg_dat_we,
+	input         reg_dat_re,
+	input  [31:0] reg_dat_di,
+	output [31:0] reg_dat_do,
+	output        reg_dat_wait
+);
+	reg [31:0] cfg_divider;
+
+	reg [3:0] recv_state;
+	reg [31:0] recv_divcnt;
+	reg [7:0] recv_pattern;
+	reg [7:0] recv_buf_data;
+	reg recv_buf_valid;
+
+	reg [9:0] send_pattern;
+	reg [3:0] send_bitcnt;
+	reg [31:0] send_divcnt;
+	reg send_dummy;
+
+	assign reg_div_do = cfg_divider;
+
+	assign reg_dat_wait = reg_dat_we && (send_bitcnt || send_dummy);
+	assign reg_dat_do = recv_buf_valid ? recv_buf_data : ~0;
+
+	always @(posedge clk) begin
+		if (!resetn) begin
+			cfg_divider <= DEFAULT_DIV;
+		end else begin
+			if (reg_div_we[0]) cfg_divider[ 7: 0] <= reg_div_di[ 7: 0];
+			if (reg_div_we[1]) cfg_divider[15: 8] <= reg_div_di[15: 8];
+			if (reg_div_we[2]) cfg_divider[23:16] <= reg_div_di[23:16];
+			if (reg_div_we[3]) cfg_divider[31:24] <= reg_div_di[31:24];
+		end
+	end
+
+	always @(posedge clk) begin
+		if (!resetn) begin
+			recv_state <= 0;
+			recv_divcnt <= 0;
+			recv_pattern <= 0;
+			recv_buf_data <= 0;
+			recv_buf_valid <= 0;
+		end else begin
+			recv_divcnt <= recv_divcnt + 1;
+			if (reg_dat_re)
+				recv_buf_valid <= 0;
+			case (recv_state)
+				0: begin
+					if (!ser_rx)
+						recv_state <= 1;
+					recv_divcnt <= 0;
+				end
+				1: begin
+					if (2*recv_divcnt > cfg_divider) begin
+						recv_state <= 2;
+						recv_divcnt <= 0;
+					end
+				end
+				10: begin
+					if (recv_divcnt > cfg_divider) begin
+						recv_buf_data <= recv_pattern;
+						recv_buf_valid <= 1;
+						recv_state <= 0;
+					end
+				end
+				default: begin
+					if (recv_divcnt > cfg_divider) begin
+						recv_pattern <= {ser_rx, recv_pattern[7:1]};
+						recv_state <= recv_state + 1;
+						recv_divcnt <= 0;
+					end
+				end
+			endcase
+		end
+	end
+
+	assign ser_tx = send_pattern[0];
+
+	always @(posedge clk) begin
+		if (reg_div_we)
+			send_dummy <= 1;
+		send_divcnt <= send_divcnt + 1;
+		if (!resetn) begin
+			send_pattern <= ~0;
+			send_bitcnt <= 0;
+			send_divcnt <= 0;
+			send_dummy <= 1;
+		end else begin
+			if (send_dummy && !send_bitcnt) begin
+				send_pattern <= ~0;
+				send_bitcnt <= 15;
+				send_divcnt <= 0;
+				send_dummy <= 0;
+			end else
+			if (reg_dat_we && !send_bitcnt) begin
+				send_pattern <= {1'b1, reg_dat_di[7:0], 1'b0};
+				send_bitcnt <= 10;
+				send_divcnt <= 0;
+			end else
+			if (send_divcnt > cfg_divider && send_bitcnt) begin
+				send_pattern <= {1'b1, send_pattern[9:1]};
+				send_bitcnt <= send_bitcnt - 1;
+				send_divcnt <= 0;
+			end
+		end
+	end
+endmodule