/*************************************************************************** Exidy 440 video system ***************************************************************************/ #include "driver.h" #include "exidy440.h" #define SPRITE_COUNT 40 /* globals */ UINT8 *exidy440_scanline; UINT8 *exidy440_imageram; UINT8 exidy440_firq_vblank; UINT8 exidy440_firq_beam; UINT8 topsecex_yscroll; /* local allocated storage */ static UINT8 exidy440_latched_x; static UINT8 *local_videoram; static UINT8 *local_paletteram; /* local variables */ static UINT8 firq_enable; static UINT8 firq_select; static UINT8 palettebank_io; static UINT8 palettebank_vis; /* function prototypes */ static void exidy440_update_firq(void); /************************************* * * Initialize the video system * *************************************/ VIDEO_START( exidy440 ) { /* reset the system */ firq_enable = 0; firq_select = 0; palettebank_io = 0; palettebank_vis = 0; exidy440_firq_vblank = 0; exidy440_firq_beam = 0; /* reset Top Secret scroll position */ topsecex_yscroll = 0; /* allocate a buffer for VRAM */ local_videoram = auto_malloc(256 * 256 * 2); memset(local_videoram, 0, 256 * 256 * 2); /* allocate a buffer for palette RAM */ local_paletteram = auto_malloc(512 * 2); memset(local_paletteram, 0, 512 * 2); } /************************************* * * Video RAM read/write * *************************************/ READ8_HANDLER( exidy440_videoram_r ) { UINT8 *base = &local_videoram[(*exidy440_scanline * 256 + offset) * 2]; /* combine the two pixel values into one byte */ return (base[0] << 4) | base[1]; } WRITE8_HANDLER( exidy440_videoram_w ) { UINT8 *base = &local_videoram[(*exidy440_scanline * 256 + offset) * 2]; /* expand the two pixel values into two bytes */ base[0] = (data >> 4) & 15; base[1] = data & 15; } /************************************* * * Palette RAM read/write * *************************************/ READ8_HANDLER( exidy440_paletteram_r ) { return local_paletteram[palettebank_io * 512 + offset]; } WRITE8_HANDLER( exidy440_paletteram_w ) { /* update palette ram in the I/O bank */ local_paletteram[palettebank_io * 512 + offset] = data; /* if we're modifying the active palette, change the color immediately */ if (palettebank_io == palettebank_vis) { int word; /* combine two bytes into a word */ offset = palettebank_vis * 512 + (offset & 0x1fe); word = (local_paletteram[offset] << 8) + local_paletteram[offset + 1]; /* extract the 5-5-5 RGB colors */ palette_set_color_rgb(Machine, offset / 2, pal5bit(word >> 10), pal5bit(word >> 5), pal5bit(word >> 0)); } } /************************************* * * Horizontal/vertical positions * *************************************/ READ8_HANDLER( exidy440_horizontal_pos_r ) { /* clear the FIRQ on a read here */ exidy440_firq_beam = 0; exidy440_update_firq(); /* according to the schems, this value is only latched on an FIRQ * caused by collision or beam */ return exidy440_latched_x; } READ8_HANDLER( exidy440_vertical_pos_r ) { int result; /* according to the schems, this value is latched on any FIRQ * caused by collision or beam, ORed together with CHRCLK, * which probably goes off once per scanline; for now, we just * always return the current scanline */ result = video_screen_get_vpos(0); return (result < 255) ? result : 255; } /************************************* * * Sprite RAM handler * *************************************/ WRITE8_HANDLER( exidy440_spriteram_w ) { video_screen_update_partial(0, video_screen_get_vpos(0)); spriteram[offset] = data; } /************************************* * * Interrupt and I/O control regs * *************************************/ WRITE8_HANDLER( exidy440_control_w ) { int oldvis = palettebank_vis; /* extract the various bits */ exidy440_bank_select(data >> 4); firq_enable = (data >> 3) & 1; firq_select = (data >> 2) & 1; palettebank_io = (data >> 1) & 1; palettebank_vis = data & 1; /* update the FIRQ in case we enabled something */ exidy440_update_firq(); /* if we're swapping palettes, change all the colors */ if (oldvis != palettebank_vis) { int i; /* pick colors from the visible bank */ offset = palettebank_vis * 512; for (i = 0; i < 256; i++, offset += 2) { /* extract a word and the 5-5-5 RGB components */ int word = (local_paletteram[offset] << 8) + local_paletteram[offset + 1]; palette_set_color_rgb(Machine, i, pal5bit(word >> 10), pal5bit(word >> 5), pal5bit(word >> 0)); } } } WRITE8_HANDLER( exidy440_interrupt_clear_w ) { /* clear the VBLANK FIRQ on a write here */ exidy440_firq_vblank = 0; exidy440_update_firq(); } /************************************* * * Interrupt generators * *************************************/ void exidy440_update_firq(void) { if (exidy440_firq_vblank || (firq_enable && exidy440_firq_beam)) cpunum_set_input_line(0, 1, ASSERT_LINE); else cpunum_set_input_line(0, 1, CLEAR_LINE); } INTERRUPT_GEN( exidy440_vblank_interrupt ) { /* set the FIRQ line on a VBLANK */ exidy440_firq_vblank = 1; exidy440_update_firq(); } /************************************* * * IRQ callback handlers * *************************************/ static TIMER_CALLBACK( beam_firq_callback ) { /* generate the interrupt, if we're selected */ if (firq_select && firq_enable) { exidy440_firq_beam = 1; exidy440_update_firq(); } /* round the x value to the nearest byte */ param = (param + 1) / 2; /* latch the x value; this convolution comes from the read routine */ exidy440_latched_x = (param + 3) ^ 2; } static TIMER_CALLBACK( collide_firq_callback ) { /* generate the interrupt, if we're selected */ if (!firq_select && firq_enable) { exidy440_firq_beam = 1; exidy440_update_firq(); } /* round the x value to the nearest byte */ param = (param + 1) / 2; /* latch the x value; this convolution comes from the read routine */ exidy440_latched_x = (param + 3) ^ 2; } /************************************* * * Sprite drawing * *************************************/ static void draw_sprites(running_machine *machine, mame_bitmap *bitmap, const rectangle *cliprect, int scroll_offset) { int i; /* get a pointer to the palette to look for collision flags */ UINT8 *palette = &local_paletteram[palettebank_vis * 512]; /* start the count high for topsecret, which doesn't use collision flags */ int count = exidy440_topsecret ? 128 : 0; /* draw the sprite images, checking for collisions along the way */ UINT8 *sprite = spriteram + (SPRITE_COUNT - 1) * 4; for (i = 0; i < SPRITE_COUNT; i++, sprite -= 4) { int image = (~sprite[3] & 0x3f); int xoffs = (~((sprite[1] << 8) | sprite[2]) & 0x1ff); int yoffs = (~sprite[0] & 0xff) + 1; int x, y, sy; UINT8 *src; /* skip if out of range */ if (yoffs < cliprect->min_y || yoffs >= cliprect->max_y + 16) continue; /* get a pointer to the source image */ src = &exidy440_imageram[image * 128]; /* account for large positive offsets meaning small negative values */ if (xoffs >= 0x1ff - 16) xoffs -= 0x1ff; /* loop over y */ sy = yoffs + scroll_offset; for (y = 0; y < 16; y++, yoffs--, sy--) { /* wrap at the top and bottom of the screen */ if (sy >= EXIDY440_VBSTART) sy -= (EXIDY440_VBSTART - EXIDY440_VBEND); else if (sy < EXIDY440_VBEND) sy += (EXIDY440_VBSTART - EXIDY440_VBEND); /* stop if we get before the current scanline */ if (yoffs < cliprect->min_y) break; /* only draw scanlines that are in this cliprect */ if (yoffs <= cliprect->max_y) { UINT8 *old = &local_videoram[sy * 512 + xoffs]; int currx = xoffs; /* loop over x */ for (x = 0; x < 8; x++, old += 2) { int ipixel = *src++; int left = ipixel & 0xf0; int right = (ipixel << 4) & 0xf0; int pen; /* left pixel */ if (left && EXIDY440_HBEND >= 0 && currx < EXIDY440_HBSTART) { /* combine with the background */ pen = left | old[0]; *BITMAP_ADDR16(bitmap, yoffs, currx) = machine->pens[pen]; /* check the collisions bit */ if ((palette[2 * pen] & 0x80) && count++ < 128) timer_set(video_screen_get_time_until_pos(0, yoffs, currx), currx, collide_firq_callback); } currx++; /* right pixel */ if (right && EXIDY440_HBEND >= 0 && currx < EXIDY440_HBSTART) { /* combine with the background */ pen = right | old[1]; *BITMAP_ADDR16(bitmap, yoffs, currx) = machine->pens[pen]; /* check the collisions bit */ if ((palette[2 * pen] & 0x80) && count++ < 128) timer_set(video_screen_get_time_until_pos(0, yoffs, currx), currx, collide_firq_callback); } currx++; } } else src += 8; } } } /************************************* * * Core refresh routine * *************************************/ static void update_screen(running_machine *machine, mame_bitmap *bitmap, const rectangle *cliprect, int scroll_offset) { int y, sy; /* draw any dirty scanlines from the VRAM directly */ sy = scroll_offset + cliprect->min_y; for (y = cliprect->min_y; y <= cliprect->max_y; y++, sy++) { /* wrap at the bottom of the screen */ if (sy >= EXIDY440_VBSTART) sy -= (EXIDY440_VBSTART - EXIDY440_VBEND); /* draw line */ draw_scanline8(bitmap, 0, y, (EXIDY440_HBSTART - EXIDY440_HBEND), &local_videoram[sy * 512], machine->pens, -1); } /* draw the sprites */ draw_sprites(machine, bitmap, cliprect, scroll_offset); } /************************************* * * Standard screen refresh callback * *************************************/ VIDEO_UPDATE( exidy440 ) { /* redraw the screen */ if (exidy440_topsecret) update_screen(machine, bitmap, cliprect, topsecex_yscroll); else update_screen(machine, bitmap, cliprect, 0); return 0; } /************************************* * * Standard screen refresh callback * *************************************/ VIDEO_EOF( exidy440 ) { /* generate an interrupt once/frame for the beam */ if (!exidy440_topsecret) { attotime time; attoseconds_t increment; int beamx, beamy; int i; beamx = ((input_port_4_r(0) & 0xff) * (EXIDY440_HBSTART - EXIDY440_HBEND)) >> 8; beamy = ((input_port_5_r(0) & 0xff) * (EXIDY440_VBSTART - EXIDY440_VBEND)) >> 8; /* The timing of this FIRQ is very important. The games look for an FIRQ and then wait about 650 cycles, clear the old FIRQ, and wait a very short period of time (~130 cycles) for another one to come in. From this, it appears that they are expecting to get beams over a 12 scanline period, and trying to pick roughly the middle one. This is how it is implemented. */ increment = attotime_to_attoseconds(video_screen_get_scan_period(0)); time = attotime_sub(video_screen_get_time_until_pos(0, beamy, beamx), attotime_make(0, increment * 6)); for (i = 0; i <= 12; i++) { timer_set(time, beamx, beam_firq_callback); time = attotime_add(time, attotime_make(0, increment)); } } }