02677: eprom, eprom2: missing graphical brightness effect, verified on real machine w/video

Note that the RGB output circuitry uses many transistors and I don't really understand it.

src/mame/drivers/eprom.c

@@ -12,6 +12,10 @@
     Known bugs:
         * none at this time
 
+    TODO:
+        * the RGB generator visible in the schematics is not properly modeled.
+
+
 ****************************************************************************
 
     Memory map (TBA)
@@ -106,13 +110,19 @@ static READ16_HANDLER( adc_r )
 
 static WRITE16_HANDLER( eprom_latch_w )
 {
-	/* reset extra CPU */
 	if (ACCESSING_BITS_0_7)
 	{
+		/* bit 0: reset extra CPU */
 		if (data & 1)
 			cpu_set_input_line(space->machine->cpu[1], INPUT_LINE_RESET, CLEAR_LINE);
 		else
 			cpu_set_input_line(space->machine->cpu[1], INPUT_LINE_RESET, ASSERT_LINE);
+
+		/* bits 1-4: screen intensity */
+		eprom_screen_intensity = (data & 0x1e) >> 1;
+
+		/* bit 5: video disable */
+		eprom_video_disable = (data & 0x20);
 	}
 }
 
@@ -164,7 +174,7 @@ static ADDRESS_MAP_START( main_map, ADDRESS_SPACE_PROGRAM, 16 )
 	AM_RANGE(0x360010, 0x360011) AM_WRITE(eprom_latch_w)
 	AM_RANGE(0x360020, 0x360021) AM_WRITE(atarigen_sound_reset_w)
 	AM_RANGE(0x360030, 0x360031) AM_WRITE(atarigen_sound_w)
-	AM_RANGE(0x3e0000, 0x3e0fff) AM_RAM_WRITE(paletteram16_IIIIRRRRGGGGBBBB_word_w) AM_BASE(&paletteram16)
+	AM_RANGE(0x3e0000, 0x3e0fff) AM_RAM AM_BASE(&paletteram16)
 	AM_RANGE(0x3f0000, 0x3f1fff) AM_WRITE(atarigen_playfield_w) AM_BASE(&atarigen_playfield)
 	AM_RANGE(0x3f2000, 0x3f3fff) AM_WRITE(atarimo_0_spriteram_w) AM_BASE(&atarimo_0_spriteram)
 	AM_RANGE(0x3f4000, 0x3f4f7f) AM_WRITE(atarigen_alpha_w) AM_BASE(&atarigen_alpha)
@@ -189,7 +199,7 @@ static ADDRESS_MAP_START( guts_map, ADDRESS_SPACE_PROGRAM, 16 )
 //  AM_RANGE(0x360010, 0x360011) AM_WRITE(eprom_latch_w)
 	AM_RANGE(0x360020, 0x360021) AM_WRITE(atarigen_sound_reset_w)
 	AM_RANGE(0x360030, 0x360031) AM_WRITE(atarigen_sound_w)
-	AM_RANGE(0x3e0000, 0x3e0fff) AM_RAM_WRITE(paletteram16_IIIIRRRRGGGGBBBB_word_w) AM_BASE(&paletteram16)
+	AM_RANGE(0x3e0000, 0x3e0fff) AM_RAM AM_BASE(&paletteram16)
 	AM_RANGE(0xff0000, 0xff1fff) AM_WRITE(atarigen_playfield_upper_w) AM_BASE(&atarigen_playfield_upper)
 	AM_RANGE(0xff8000, 0xff9fff) AM_WRITE(atarigen_playfield_w) AM_BASE(&atarigen_playfield)
 	AM_RANGE(0xffa000, 0xffbfff) AM_WRITE(atarimo_0_spriteram_w) AM_BASE(&atarimo_0_spriteram)

src/mame/includes/eprom.h

@@ -13,3 +13,6 @@ VIDEO_START( guts );
 VIDEO_UPDATE( guts );
 
 void eprom_scanline_update(const device_config *screen, int scanline);
+
+extern int eprom_screen_intensity;
+extern int eprom_video_disable;

src/mame/video/eprom.c

@@ -10,6 +10,44 @@
 #include "thunderj.h"
 
 
+int eprom_screen_intensity;
+int eprom_video_disable;
+
+
+/*************************************
+ *
+ *  Palette
+ *
+ *************************************/
+
+static void update_palette(running_machine *machine)
+{
+	int color;
+
+	for (color = 0; color < 0x800; ++color)
+	{
+		int i, r, g, b;
+		UINT16 const data = paletteram16[color];
+
+		/* FIXME this is only a very crude approximation of the palette output.
+		 * The circuit involves a dozen transistors and probably has an output
+		 * which is quite different from this.
+		 * This is, however, good enough to match the video and description
+		 * of MAMETesters bug #02677.
+		 */
+		i = (((data >> 12) & 15) + 1) * (4 - eprom_screen_intensity);
+		if (i < 0)
+			i = 0;
+
+		r = ((data >> 8) & 15) * i / 4;
+		g = ((data >> 4) & 15) * i / 4;
+		b = ((data >> 0) & 15) * i / 4;
+
+		palette_set_color_rgb(machine, color, r, g, b);
+	}
+}
+
+
 
 /*************************************
  *
@@ -102,6 +140,12 @@ VIDEO_START( eprom )
 	/* initialize the alphanumerics */
 	atarigen_alpha_tilemap = tilemap_create(get_alpha_tile_info, tilemap_scan_rows,  8,8, 64,32);
 	tilemap_set_transparent_pen(atarigen_alpha_tilemap, 0);
+
+	/* global brightess (not used by klax and guts) */
+	eprom_screen_intensity = 0;
+
+	/* video disabled (not used?) */
+	eprom_video_disable = 0;
 }
 
 
@@ -153,6 +197,12 @@ VIDEO_START( guts )
 	/* initialize the alphanumerics */
 	atarigen_alpha_tilemap = tilemap_create(get_alpha_tile_info, tilemap_scan_rows,  8,8, 64,32);
 	tilemap_set_transparent_pen(atarigen_alpha_tilemap, 0);
+
+	/* global brightess (not used by guts) */
+	eprom_screen_intensity = 0;
+
+	/* video disable (not used by guts) */
+	eprom_video_disable = 0;
 }
 
 
@@ -191,6 +241,14 @@ VIDEO_UPDATE( eprom )
 	bitmap_t *mobitmap;
 	int x, y, r;
 
+	if (eprom_video_disable)
+	{
+		bitmap_fill(bitmap,cliprect,get_black_pen(screen->machine));
+		return 0;
+	}
+
+	update_palette(screen->machine);
+
 	/* draw the playfield */
 	tilemap_draw(bitmap, cliprect, atarigen_playfield_tilemap, 0, 0);
 
@@ -337,6 +395,14 @@ VIDEO_UPDATE( guts )
 	bitmap_t *mobitmap;
 	int x, y, r;
 
+	if (eprom_video_disable)
+	{
+		bitmap_fill(bitmap,cliprect,get_black_pen(screen->machine));
+		return 0;
+	}
+
+	update_palette(screen->machine);
+
 	/* draw the playfield */
 	tilemap_draw(bitmap, cliprect, atarigen_playfield_tilemap, 0, 0);