From b739fae4ecd00c3e1753b2c68dbfef2a46c659a8 Mon Sep 17 00:00:00 2001
From: Till Harbaum <till@harbaum.org>
Date: Fri, 9 Oct 2015 09:53:27 +0200
Subject: [PATCH] [BBC] Autoboot option

---
 cores/bbc/fpga/mist/bbc_mist_top.v | 22 ++++++++++++++++++----
 cores/bbc/rtl/bbc.v                |  4 ++++
 cores/bbc/rtl/keyboard.v           |  8 ++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/cores/bbc/fpga/mist/bbc_mist_top.v b/cores/bbc/fpga/mist/bbc_mist_top.v
index 6b9f744..a3fd38a 100644
--- a/cores/bbc/fpga/mist/bbc_mist_top.v
+++ b/cores/bbc/fpga/mist/bbc_mist_top.v
@@ -50,10 +50,11 @@ parameter CONF_STR = {
         "BBC;ROM;",
         "O1,Scanlines,Off,On;",
         "O2,ROM mapping,High,Low;",
-        "T3,Reset;"
+        "O3,Auto boot,Off,On;",
+        "T4,Reset;"
 };
 
-parameter CONF_STR_LEN = 8+20+24+9;
+parameter CONF_STR_LEN = 8+20+24+20+9;
 
 // generated clocks
 wire clk_32m /* synthesis keep */ ;
@@ -270,14 +271,25 @@ wire rom_remap_reset = (rom_map_counter != 0);
 // the bbc is being reset of the pll isn't stable, if the ram isn't ready,
 // of the arm boots or if the user selects reset from the osd or of the user
 // presses the "core" button or the io controller uploads a rom
-wire reset_in = ~pll_ready || ~sdram_ready || status[0] || status[3] ||
+wire reset_in = ~pll_ready || ~sdram_ready || status[0] || status[4] ||
 		buttons[1] || loader_active || rom_remap_reset;
 
 // synchronize reset with memory state machine
 reg reset;
 always @(posedge mem_sync)
 	reset <= reset_in;
-		
+
+// the autoboot feature simply works by pressing shift for 2 seconds after 
+// the bbc has been reset
+wire autoboot_shift = status[3] && (autoboot_counter != 0 );
+reg [24:0] autoboot_counter;
+always @(posedge clk_32m) begin
+	if(reset) 
+		autoboot_counter <= 25'd32000000;
+	else if(autoboot_counter != 0)
+		autoboot_counter <= autoboot_counter - 25'd1;
+end
+
 bbc BBC(
 	
 	.CLK32M_I	( clk_32m		),
@@ -303,6 +315,8 @@ bbc BBC(
     .VID_ADR    ( vid_adr       ),
     .VID_DI     ( vid_data      ),
 	
+    .SHIFT     ( autoboot_shift ),
+	
 	 .user_via_pb_out ( user_via_pb_out   ),
 	 .user_via_cb1_in ( user_via_cb1_in   ),
 	 .user_via_cb2_in ( user_via_cb2_in   ),
diff --git a/cores/bbc/rtl/bbc.v b/cores/bbc/rtl/bbc.v
index 64da6c3..1e3ca25 100644
--- a/cores/bbc/rtl/bbc.v
+++ b/cores/bbc/rtl/bbc.v
@@ -36,6 +36,9 @@ module bbc(
 	output [15:0]	AUDIO_L,
 	output [15:0]	AUDIO_R,
 
+	// externally pressed "shift" key for autoboot
+	input          SHIFT,
+	
 	// expose pins required for mmc
 	output [7:0]   user_via_pb_out,
 	input          user_via_cb1_in,
@@ -372,6 +375,7 @@ keyboard KEYB (
 	 .ROW				( keyb_row		),
 	 .KEYPRESS		( keyb_out		),
 	 .INT				( keyb_int		),
+	 .SHIFT        ( SHIFT        ),
 	 .BREAK_OUT		( keyb_break	),
 	 .DIP_SWITCH	( DIP_SWITCH	)
 );
diff --git a/cores/bbc/rtl/keyboard.v b/cores/bbc/rtl/keyboard.v
index cce8fcc..b36c0a3 100644
--- a/cores/bbc/rtl/keyboard.v
+++ b/cores/bbc/rtl/keyboard.v
@@ -50,6 +50,8 @@ module keyboard (
 		input   [2:0] ROW,
 		output   KEYPRESS,
 		output   INT,
+		// external SHIFT key
+		input    SHIFT,
 		//  BREAK key output - 1 when pressed
 		output reg  BREAK_OUT,
 		//  DIP switch inputs
@@ -67,6 +69,7 @@ reg     [7:0] keys [0:15];
 reg     [3:0] col;
 reg     _release_;
 reg     extended;
+reg     ext_shift;
 
 //  Shortcut to current key column
 
@@ -144,6 +147,11 @@ always @(posedge CLOCK) begin
 		
     end else  begin
 
+		  // map external shift key onto left shift
+		  ext_shift <= SHIFT;
+		  if(SHIFT || ext_shift)
+				keys[0][0] <= SHIFT;
+
         //  Copy DIP switches through to row 0
         keys[2][0] <= DIP_SWITCH[7];
         keys[3][0] <= DIP_SWITCH[6];