From 75378b13bdfb77ceb6e91bca09801afef7122184 Mon Sep 17 00:00:00 2001
From: Tomek Malesinski <tmal@mimuw.edu.pl>
Date: Mon, 1 Sep 2008 23:42:39 +0200
Subject: [PATCH] Serial input/output in Pokey

---
 pokey.v | 54 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 10 deletions(-)

diff --git a/pokey.v b/pokey.v
index 68c7360..e7e3d33 100644
--- a/pokey.v
+++ b/pokey.v
@@ -187,7 +187,9 @@ module pokey(rst_i, clk_i,
 	     ack_o,
 	     irq,
 	     audout,
-	     key_code, key_pressed, key_shift, key_break);
+	     key_code, key_pressed, key_shift, key_break,
+	     serout, serout_rdy_o, serout_ack_i,
+	     serin, serin_rdy_i, serin_ack_o);
    input rst_i;
    input clk_i;
    input adr_i;
@@ -195,11 +197,13 @@ module pokey(rst_i, clk_i,
    input we_i;
    input stb_i;
    input key_code, key_pressed, key_shift, key_break;
+   input serout_ack_i, serin, serin_rdy_i;
 
    output dat_o;
    output ack_o;
    output irq;
    output audout;
+   output serout, serout_rdy_o, serin_ack_o;
 
    wire       rst_i, clk_i;
    wire [3:0] adr_i;
@@ -215,6 +219,15 @@ module pokey(rst_i, clk_i,
 
    wire [5:0] audout = audout0 + audout1 + audout2 + audout3;
    
+   wire [7:0] serin;
+   wire       serin_rdy_i;
+   reg 	      last_serin_rdy_i;
+   reg 	      serin_ack_o;
+   reg [7:0]  serout;
+   reg 	      serout_rdy_o;
+   wire       serout_ack_i;
+   reg 	      last_serout_ack_i;
+
    wire       rst = (rst_bits == 0);
    wire       start_timer;
 
@@ -264,7 +277,8 @@ module pokey(rst_i, clk_i,
 
    assign     ack_o = stb_i;
 
-   always @ (adr_i or random)
+   always @ (adr_i or key_code or random or serin or irqst or irqen or
+	     key_shift or key_pressed)
      if (adr_i == 'h9)
        // KBCODE
        dat_o = key_code;
@@ -272,8 +286,8 @@ module pokey(rst_i, clk_i,
        // RANDOM
        dat_o = random;
      else if (adr_i == 'hd)
-       // TODO: SERIN
-       dat_o = 'hff;
+       // SERIN
+       dat_o = serin;
      else if (adr_i == 'he)
        // IRQST
        dat_o = ~(irqst & irqen);
@@ -317,11 +331,27 @@ module pokey(rst_i, clk_i,
 	// TODO: reset SKSTAT[7:5] if they are implemented
      end
 
+   always @ (posedge clk_i) begin
+      last_serin_rdy_i <= serin_rdy_i;
+      if (rst)
+	serin_ack_o <= 0;
+      else if (stb_i && !we_i && adr_i == 'hd && serin_rdy_i)
+	serin_ack_o <= 1;
+      else if (!serin_rdy_i)
+	serin_ack_o <= 0;
+   end
+
    // SEROUT
-   always @ (posedge clk_i)
-     if (we_i && stb_i && adr_i == 'hd) begin
-	// TODO: serial output
-     end
+   always @ (posedge clk_i) begin
+      last_serout_ack_i <= serout_ack_i;
+      if (rst)
+	serout_rdy_o <= 0;
+      else if (we_i && stb_i && adr_i == 'hd) begin
+	 serout <= dat_i;
+	 serout_rdy_o <= 1;
+      end else if (serout_ack_i)
+	serout_rdy_o <= 0;
+   end
 
    // IRQEN
    always @ (posedge clk_i)
@@ -341,10 +371,14 @@ module pokey(rst_i, clk_i,
 
    always @ (posedge clk_i)
      // IRQ_SERFIN has no latch.
-     irqst <= irqen & ({irqst[7:4], 1'b0, irqst[2:0]} |
+     irqst <= irqen & ({irqst[7:4],
+			!serout_ack_i && !serout_rdy_o,
+			irqst[2:0]} |
 		       {key_break && !last_key_break,
 			key_pressed && !last_key_pressed,
-			3'b000, borrow[3], borrow[1:0]});
+			serin_rdy_i && !last_serin_rdy_i,
+			serout_ack_i && !last_serout_ack_i,
+			1'b0, borrow[3], borrow[1:0]});
 
    always @ (irqst) begin
       irq = 0;
-- 
2.11.4.GIT