Phil_B figured out why dirtdash locks up, send beer

src/mame/drivers/namcos22.c

@@ -2588,7 +2588,7 @@ static ADDRESS_MAP_START( namcos22s_am, AS_PROGRAM, 32 )
 	AM_RANGE(0x89e000, 0x89ffff) AM_READWRITE(namcos22_textram_r, namcos22_textram_w) AM_BASE_MEMBER(namcos22_state, m_textram)
 	AM_RANGE(0x8a0000, 0x8a000f) AM_READWRITE(namcos22_tilemapattr_r, namcos22_tilemapattr_w) AM_BASE_MEMBER(namcos22_state, m_tilemapattr)
 	AM_RANGE(0x900000, 0x90ffff) AM_RAM AM_BASE_MEMBER(namcos22_state, m_vics_data)
-	AM_RANGE(0x940000, 0x94007f) AM_RAM AM_BASE_MEMBER(namcos22_state, m_vics_control)
+	AM_RANGE(0x940000, 0x94007f) AM_READWRITE(namcos22s_vics_control_r, namcos22s_vics_control_w) AM_BASE_MEMBER(namcos22_state, m_vics_control)
 	AM_RANGE(0x980000, 0x9affff) AM_RAM AM_BASE_MEMBER(namcos22_state, m_spriteram) /* C374 */
 	AM_RANGE(0xa04000, 0xa0bfff) AM_READWRITE(namcos22_mcuram_r, namcos22_mcuram_w) AM_BASE_MEMBER(namcos22_state, m_shareram) /* COM RAM */
 	AM_RANGE(0xc00000, 0xc1ffff) AM_READWRITE(namcos22_dspram_r, namcos22_dspram_w) AM_BASE_MEMBER(namcos22_state, m_polygonram)
@@ -5772,7 +5772,7 @@ GAME( 1994, alpinerd, 0,         namcos22s, alpiner,  alpiner,  ROT0, "Namco", "
 GAME( 1994, alpinerc, alpinerd,  namcos22s, alpiner,  alpiner,  ROT0, "Namco", "Alpine Racer (Rev. AR2 Ver.C)"             , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS )
 GAME( 1995, airco22b, 0,         namcos22s, airco22,  airco22,  ROT0, "Namco", "Air Combat 22 (Rev. ACS1 Ver.B, Japan)"    , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS|GAME_NOT_WORKING ) // boots but missing sprite clear DMA?
 GAME( 1995, cybrcycc, 0,         namcos22s, cybrcycc, cybrcyc,  ROT0, "Namco", "Cyber Cycles (Rev. CB2 Ver.C)"             , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS ) // 95/04/04
-GAME( 1995, dirtdash, 0,         namcos22s, dirtdash, dirtdash, ROT0, "Namco", "Dirt Dash (Rev. DT2)"                      , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS|GAME_NOT_WORKING ) // 95/12/20 20:01:56. locks up, dsp comms/slave dsp? - romdump looks fine
+GAME( 1995, dirtdash, 0,         namcos22s, dirtdash, dirtdash, ROT0, "Namco", "Dirt Dash (Rev. DT2)"                      , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS|GAME_NOT_WORKING ) // 95/12/20 20:01:56. many issues: slowdown, missing sprites, text layer transparency, spot ram
 GAME( 1995, timecris, 0,         namcos22s, timecris, timecris, ROT0, "Namco", "Time Crisis (Rev. TS2 Ver.B)"              , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS ) // 96/04/02 18:48:00
 GAME( 1995, timecrisa,timecris,  namcos22s, timecris, timecris, ROT0, "Namco", "Time Crisis (Rev. TS2 Ver.A)"              , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS ) // 96/01/08 18:56:09
 GAME( 1996, propcycl, 0,         namcos22s, propcycl, propcycl, ROT0, "Namco", "Prop Cycle (Rev. PR2 Ver.A)"               , GAME_IMPERFECT_SOUND|GAME_IMPERFECT_GRAPHICS ) // 96/06/18 21:22:13

src/mame/includes/namcos22.h

@@ -126,6 +126,9 @@ WRITE32_HANDLER( namcos22_paletteram_w );
 READ32_HANDLER( namcos22_textram_r );
 WRITE32_HANDLER( namcos22_textram_w );
 
+READ32_HANDLER( namcos22s_vics_control_r );
+WRITE32_HANDLER( namcos22s_vics_control_w );
+
 READ32_HANDLER( namcos22_gamma_r );
 WRITE32_HANDLER( namcos22_gamma_w );
 

src/mame/video/namcos22.c

@@ -4,10 +4,11 @@
  * todo (ordered by importance):
  *
  * - emulate slave dsp!
- * - emulate spot
+ * - emulate spot (see testmode and dirtdash)
  * - texture u/v mapping is often 1 pixel off, resulting in many glitch lines/gaps between textures
  * - tokyowar tanks are not shootable, same for timecris helicopter, there's still a very small hitbox but almost impossible to hit
  *       (is this related to dsp? or cpu?)
+ * - no sprites shown in dirtdash
  * - eliminate sprite garbage in airco22b: find out how/where vics num_sprites is determined exactly, or is it linktable related?
  * - window clipping (acedrvrw, victlapw)
  * - using rgbint to set brightness may cause problems if a color channel is 00 (eg. victlapw attract)
@@ -1699,16 +1700,16 @@ DrawSprites( running_machine &machine, bitmap_t *bitmap, const rectangle *clipre
 
 	/* VICS RAM provides two additional banks (also many unknown regs here) */
 	/*
-    0x940000 -x------       sprite chip busy
+    0x940000 -x------       sprite chip busy?
     0x940018 xxxx----       clr.w   $940018.l
 
     0x940030 xxxxxxxx       0x0600000 - enable bits?
     0x940034 xxxxxxxx       0x3070b0f
 
-    0x940040 xxxxxxxx       sprite attribute size
+    0x940040 xxxxxxxx       sprite attribute size             high bit means busy?
-    0x940048 xxxxxxxx       sprite attribute list baseaddr
+    0x940048 xxxxxxxx       sprite attribute list baseaddr    high bit means busy?
-    0x940050 xxxxxxxx       sprite color size
+    0x940050 xxxxxxxx       sprite color size                 high bit means busy?
-    0x940058 xxxxxxxx       sprite color list baseaddr
+    0x940058 xxxxxxxx       sprite color list baseaddr        high bit means busy?
 
     0x940060..0x94007c      set#2
     */
@@ -1730,6 +1731,38 @@ DrawSprites( running_machine &machine, bitmap_t *bitmap, const rectangle *clipre
 	}
 } /* DrawSprites */
 
+READ32_HANDLER( namcos22s_vics_control_r )
+{
+	namcos22_state *state = space->machine().driver_data<namcos22_state>();
+	UINT32 ret = state->m_vics_control[offset];
+
+	switch (offset*4)
+	{
+		// reg 0, status register?
+		// high byte is read in timecris and lower half is expected to be 0
+		case 0x00:
+			ret = 0;
+			break;
+
+		// sprite attr/color size regs: high bit is busy/ready?
+		// dirtdash reads these and waits for it to become 0
+		case 0x40: case 0x50: case 0x60: case 0x70:
+			ret &= 0x7fffffff;
+			break;
+
+		default:
+			break;
+	}
+	return ret;
+}
+
+WRITE32_HANDLER( namcos22s_vics_control_w )
+{
+	namcos22_state *state = space->machine().driver_data<namcos22_state>();
+	COMBINE_DATA(&state->m_vics_control[offset]);
+}
+
+
 static void UpdatePalette(running_machine &machine)
 {
 	namcos22_state *state = machine.driver_data<namcos22_state>();