video_formatter: fix secondary palette access/display selection, clean up some fluff

video_formatter.v

@@ -3,7 +3,7 @@
  * MNT ZZ9000 Amiga Graphics and Coprocessor Card Firmware
  * Video Stream Formatter
  *
- * Copyright (C) 2019-2020, Lukas F. Hartmann <lukas@mntre.com>
+ * Copyright (C) 2019-2021, Lukas F. Hartmann <lukas@mntre.com>
  *                          MNT Research GmbH, Berlin
  *                          https://mntre.com
  *
@@ -55,15 +55,16 @@ localparam OP_SPRITE_ADDR=14;
 localparam OP_SPRITE_DATA=15;
 localparam OP_VIDEOCAP=16; // we ignore this here, it's snooped by MNTZorro
 localparam OP_REPORT_LINE=17;
-localparam OP_PALETTE_SEL=18; // access secondary 256 colors for screen split
+localparam OP_PALETTE_SEL=18; // switch display to secondary 256 color palette for screen split
+localparam OP_PALETTE_HI=19; // set values in secondary 256 color palette for screen split
 
 localparam CMODE_8BIT=0;
 localparam CMODE_16BIT=1;
 localparam CMODE_32BIT=2;
 localparam CMODE_15BIT=4;
 
-reg [11:0] screen_width; // = 720;
-reg [11:0] screen_height; // = 576;
+reg [11:0] screen_width;
+reg [11:0] screen_height;
 reg scale_x = 0;
 reg scale_y = 1; // amiga boots in 640x256, so double the resolution vertically
 reg [23:0] palette[511:0];
@@ -72,12 +73,12 @@ reg vsync_request;
 reg sync_polarity = 1; // negative polarity
 reg selected_palette = 0;
 
-reg [15:0] screen_h_max; //= 864;
-reg [15:0] screen_v_max; //= 625;
-reg [15:0] screen_h_sync_start; //= 732;
-reg [15:0] screen_h_sync_end; //= 796;
-reg [15:0] screen_v_sync_start; //= 581;
-reg [15:0] screen_v_sync_end; //= 586;
+reg [15:0] screen_h_max;
+reg [15:0] screen_v_max;
+reg [15:0] screen_h_sync_start;
+reg [15:0] screen_h_sync_end;
+reg [15:0] screen_v_sync_start;
+reg [15:0] screen_v_sync_end;
 
 localparam MAXWIDTH=1280;
 reg [31:0] line_buffer[MAXWIDTH-1:0];
@@ -221,7 +222,8 @@ begin
   end
 
   case (control_op_in)
-    OP_PALETTE: palette[{selected_palette, control_data_in[31:24]}] <= control_data_in[23:0];
+    OP_PALETTE: palette[{1'b0, control_data_in[31:24]}] <= control_data_in[23:0];
+    OP_PALETTE_HI: palette[{1'b1, control_data_in[31:24]}] <= control_data_in[23:0];
     OP_PALETTE_SEL: selected_palette <= control_data_in[0];
     OP_DIMENSIONS: begin
         screen_height <= control_data_in[31:16];
@@ -252,18 +254,7 @@ begin
         sync_polarity <= control_data_in[0];
       end
     OP_RESET: begin
-        /*sync_polarity <= 1;
-        screen_h_max <= 864;
-        screen_v_max <= 625;
-        screen_h_sync_start <= 732;
-        screen_h_sync_end <= 796;
-        screen_v_sync_start <= 581;
-        screen_v_sync_end <= 586;
-        scale_x <= 0;
-        scale_y <= 1;
-        screen_width <= 720;
-        screen_height <= 576;
-        colormode <= CMODE_32BIT;*/
+      /* currently a NOP */
       end
     OP_SPRITEXY: begin
         sprite_y <= control_data_in[31:16];