From: Marius Gavrilescu <marius@ieval.ro>
Date: Mon, 19 Mar 2018 14:22:16 +0000 (+0200)
Subject: Write writer.v in more combinational style
X-Git-Url: http://git.ieval.ro/?p=yule.git;a=commitdiff_plain;h=3e43ab7c61611bc7047c1d5285f8915099928d97

Write writer.v in more combinational style
---

diff --git a/writer.v b/writer.v
index c53d89f..8ac04ac 100644
--- a/writer.v
+++ b/writer.v
@@ -1,54 +1,70 @@
-`define STATE_START        2'b00
-`define STATE_WRITE1       2'b01
-`define STATE_WRITE2       2'b10
-`define STATE_INCREMENT    2'b11
-
-module WRITER (input clk, input clk_enable, output reg [7:0] tx_byte, output reg tx_signal = 0, input tx_busy, output reg finished = 0, output [12:0] ram_addr, input [15:0] ram_do, input [12:0] freeptr);
-   reg [1:0] state = `STATE_START;
+`define STATE_START        3'b000
+`define STATE_WRITE1_WAIT  3'b001
+`define STATE_WRITE1       3'b010
+`define STATE_WRITE2_WAIT  3'b011
+`define STATE_WRITE2       3'b100
+`define STATE_INCREMENT    3'b101
+`define STATE_FINISHED     3'b111
 
+module WRITER (input clk, input clk_enable, output [7:0] tx_byte, output tx_signal, input tx_busy, output finished, output [12:0] ram_addr, input [15:0] ram_do, input [12:0] freeptr);
+   reg [2:0] state = `STATE_START;
    reg [12:0] current_index;
 
    assign ram_addr = current_index;
+   assign finished = state == `STATE_FINISHED;
+
+   always @* begin
+	  case(state)
+		`STATE_WRITE1: begin
+		   tx_signal <= 1;
+		   tx_byte   <= ram_do[15:8];
+		end
+
+		`STATE_WRITE2: begin
+		   tx_signal <= 1;
+		   tx_byte   <= ram_do[7:0];
+		end
+
+		default: begin
+		   tx_signal <= 0;
+		   tx_byte   <= 12'dx;
+		end
+	  endcase
+   end
 
    always @ (posedge clk) begin
 	 if (clk_enable) begin
-		if(tx_signal)
-		  tx_signal <= 0;
-
 		case(state)
 		  `STATE_START: begin
 			 current_index <= 4;
-			 state <= `STATE_WRITE1;
+			 state <= `STATE_WRITE1_WAIT;
 		  end
 
-		  `STATE_WRITE1: begin
-			 if(!tx_busy && !tx_signal) begin
-				tx_signal <= 1;
-				tx_byte <= ram_do[15:8];
-				state <= `STATE_WRITE2;
-			 end
+		  `STATE_WRITE1_WAIT: begin
+			 if(!tx_busy) state <= `STATE_WRITE1;
 		  end
 
-		  `STATE_WRITE2: begin
-			 if(!tx_busy && !tx_signal) begin
-				tx_signal <= 1;
-				tx_byte <= ram_do[7:0];
-				state <= `STATE_INCREMENT;
-			 end
+		  `STATE_WRITE1: state <= `STATE_WRITE2_WAIT;
+
+		  `STATE_WRITE2_WAIT: begin
+			 if(!tx_busy) state <= `STATE_WRITE2;
 		  end
 
+		  `STATE_WRITE2: state <= `STATE_INCREMENT;
+
 		  `STATE_INCREMENT: begin
 			 current_index <= current_index + 1;
 			 if(current_index >= freeptr) begin
-				finished <= 1;
-				state <= `STATE_START;
+				state <= `STATE_FINISHED;
 			 end else begin
-				state <= `STATE_WRITE1;
+				state <= `STATE_WRITE1_WAIT;
 			 end
 		  end
+
+		  `STATE_FINISHED: state <= `STATE_START;
+
+		  default: state <= `STATE_START;
 		endcase // case (state)
 	 end // if (clk_enable)
-	 else
-	   finished <= 0;
    end
 endmodule