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4eb8d17acf
Genesis-Plus-GX/source/vdp.c
ekeeke31 4eb8d17acf [-]removed Gens YM2612 core support 
[~]fixed YM2612 context restore 
[+]improved YM2612 emulation accuracy (BROKEN)
2009-02-25 16:53:28 +00:00

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/***************************************************************************************
* Genesis Plus 1.2a
* Video Display Processor (memory handlers)
*
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Charles Mac Donald (original code)
* modified by Eke-Eke (compatibility fixes & additional code), GC/Wii port
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
****************************************************************************************/
#include "shared.h"
#include "hvc.h"
/* Pack and unpack CRAM data */
#define PACK_CRAM(d) ((((d)&0xE00)>>9)|(((d)&0x0E0)>>2)|(((d)&0x00E)<<5))
#define UNPACK_CRAM(d) ((((d)&0x1C0)>>5)|((d)&0x038)<<2|(((d)&0x007)<<9))
/* Mark a pattern as dirty */
#define MARK_BG_DIRTY(addr) \
{ \
name = (addr >> 5) & 0x7FF; \
if(bg_name_dirty[name] == 0) bg_name_list[bg_list_index++] = name; \
bg_name_dirty[name] |= (1 << ((addr >> 2) & 0x07)); \
}
/* VDP context */
uint8 sat[0x400]; /* Internal copy of sprite attribute table */
uint8 vram[0x10000]; /* Video RAM (64Kx8) */
uint8 cram[0x80]; /* On-chip color RAM (64x9) */
uint8 vsram[0x80]; /* On-chip vertical scroll RAM (40x11) */
uint8 reg[0x20]; /* Internal VDP registers (23x8) */
uint16 addr; /* Address register */
uint16 addr_latch; /* Latched A15, A14 of address */
uint8 code; /* Code register */
uint8 pending; /* Pending write flag */
uint16 status; /* VDP status flags */
uint8 dmafill; /* next VDP Write is DMA Fill */
uint8 hint_pending; /* 0= Line interrupt is pending */
uint8 vint_pending; /* 1= Frame interrupt is pending */
uint16 irq_status; /* Interrupt lines updated */
/* Global variables */
uint16 ntab; /* Name table A base address */
uint16 ntbb; /* Name table B base address */
uint16 ntwb; /* Name table W base address */
uint16 satb; /* Sprite attribute table base address */
uint16 hscb; /* Horizontal scroll table base address */
uint8 border; /* Border color index */
uint8 bg_name_dirty[0x800]; /* 1= This pattern is dirty */
uint16 bg_name_list[0x800]; /* List of modified pattern indices */
uint16 bg_list_index; /* # of modified patterns in list */
uint8 bg_pattern_cache[0x80000]; /* Cached and flipped patterns */
uint8 playfield_shift; /* Width of planes A, B (in bits) */
uint8 playfield_col_mask; /* Vertical scroll mask */
uint16 playfield_row_mask; /* Horizontal scroll mask */
uint32 y_mask; /* Name table Y-index bits mask */
uint16 hc_latch; /* latched HCounter (INT2) */
uint16 v_counter; /* VDP scanline counter */
uint32 dma_length; /* Current DMA remaining bytes */
int32 fifo_write_cnt; /* VDP writes fifo count */
uint32 fifo_lastwrite; /* last VDP write cycle */
uint8 fifo_latency; /* VDP write cycles latency */
uint8 odd_frame; /* 1: odd field, 0: even field */
uint8 im2_flag; /* 1= Interlace mode 2 is being used */
uint8 interlaced; /* 1: Interlaced mode 1 or 2 */
uint8 vdp_pal = 0; /* 1: PAL , 0: NTSC (default) */
uint8 vdp_rate; /* PAL: 50hz, NTSC: 60hz */
uint16 lines_per_frame; /* PAL: 313 lines, NTSC: 262 lines */
/* Tables that define the playfield layout */
static const uint8 shift_table[] = { 6, 7, 0, 8 };
static const uint8 col_mask_table[] = { 0x0F, 0x1F, 0x0F, 0x3F };
static const uint16 row_mask_table[] = { 0x0FF, 0x1FF, 0x2FF, 0x3FF };
static const uint32 y_mask_table[] = { 0x1FC0, 0x1F80, 0x1FC0, 0x1F00 };
static uint16 sat_base_mask; /* Base bits of SAT */
static uint16 sat_addr_mask; /* Index bits of SAT */
static uint32 dma_endCycles; /* 68k cycles to DMA end */
static uint8 dma_type; /* Type of DMA */
/* DMA Timings
According to the manual, here's a table that describes the transfer
rates of each of the three DMA types:
DMA Mode Width Display Transfer Count
-----------------------------------------------------
68K > VDP 32-cell Active 16
Blanking 167
40-cell Active 18
Blanking 205
VRAM Fill 32-cell Active 15
Blanking 166
40-cell Active 17
Blanking 204
VRAM Copy 32-cell Active 8
Blanking 83
40-cell Active 9
Blanking 102
'Active' is the active display period, 'Blanking' is either the vertical
blanking period or when the display is forcibly blanked via register #1.
The above transfer counts are all in bytes, unless the destination is
CRAM or VSRAM for a 68K > VDP transfer, in which case it is in words.
*/
static const uint32 dma_rates[16] = {
8, 83, 9, 102, /* 68K to VRAM (1 word = 2 bytes) */
16, 167, 18, 205, /* 68K to CRAM or VSRAM */
15, 166, 17, 204, /* DMA fill */
8, 83, 9, 102, /* DMA Copy */
};
/* Function prototypes */
static inline void data_write(unsigned int data);
static inline void vdp_reg_w(unsigned int r, unsigned int d);
/*--------------------------------------------------------------------------*/
/* Init, reset, shutdown functions */
/*--------------------------------------------------------------------------*/
void vdp_init(void)
{
/* PAL/NTSC timings */
vdp_rate = vdp_pal ? 50 : 60;
lines_per_frame = vdp_pal ? 313 : 262;
}
void vdp_reset(void)
{
memset ((char *) sat, 0, sizeof (sat));
memset ((char *) vram, 0, sizeof (vram));
memset ((char *) cram, 0, sizeof (cram));
memset ((char *) vsram, 0, sizeof (vsram));
memset ((char *) reg, 0, sizeof (reg));
addr = 0;
addr_latch = 0;
code = 0;
pending = 0;
status = 0x200; /* fifo empty */
status |= vdp_pal;
ntab = 0;
ntbb = 0;
ntwb = 0;
satb = 0;
hscb = 0;
sat_base_mask = 0xFE00;
sat_addr_mask = 0x01FF;
border = 0x00;
memset ((char *) bg_name_dirty, 0, sizeof (bg_name_dirty));
memset ((char *) bg_name_list, 0, sizeof (bg_name_list));
bg_list_index = 0;
memset ((char *) bg_pattern_cache, 0, sizeof (bg_pattern_cache));
playfield_shift = 6;
playfield_col_mask = 0x0F;
playfield_row_mask = 0x0FF;
y_mask = 0x1FC0;
hint_pending = 0;
vint_pending = 0;
irq_status = 0;
hc_latch = 0;
v_counter = 0;
dmafill = 0;
dma_length = 0;
dma_endCycles = 0;
im2_flag = 0;
interlaced = 0;
odd_frame = 0;
fifo_write_cnt = 0;
/* reset HVC tables */
vctab = (vdp_pal) ? vc_pal_224 : vc_ntsc_224;
hctab = cycle2hc32;
/* reset display area */
bitmap.viewport.w = 256;
bitmap.viewport.h = 224;
bitmap.viewport.oh = 256;
bitmap.viewport.ow = 224;
/* reset border area */
bitmap.viewport.x = config.overscan ? 12 : 0;
bitmap.viewport.y = config.overscan ? (vdp_pal ? 32 : 8) : 0;
bitmap.viewport.changed = 1;
/* initialize some registers (normally set by BIOS) */
if (config.bios_enabled != 3)
{
vdp_reg_w(1 , 0x04); /* Mode 5 enabled */
vdp_reg_w(10, 0xff); /* HINT disabled */
vdp_reg_w(12, 0x81); /* H40 mode */
vdp_reg_w(15, 0x02); /* auto increment */
window_clip(1,0);
}
/* default latency */
fifo_latency = 27;
}
void vdp_shutdown(void)
{}
void vdp_restore(uint8 *vdp_regs)
{
int i;
for (i=0;i<0x20;i++)
{
vdp_reg_w(i, vdp_regs[i]);
}
/* reinitialize HVC tables */
vctab = (vdp_pal) ? ((reg[1] & 8) ? vc_pal_240 : vc_pal_224) : vc_ntsc_224;
hctab = (reg[12] & 1) ? cycle2hc40 : cycle2hc32;
/* reinitialize overscan area */
bitmap.viewport.x = config.overscan ? ((reg[12] & 1) ? 16 : 12) : 0;
bitmap.viewport.y = config.overscan ? (((reg[1] & 8) ? 0 : 8) + (vdp_pal ? 24 : 0)) : 0;
bitmap.viewport.changed = 1;
/* restore VDP timings */
fifo_latency = (reg[12] & 1) ? 27 : 30;
if ((code & 0x0F) == 0x01) fifo_latency = fifo_latency * 2;
/* remake cache */
for (i=0;i<0x800;i++)
{
bg_name_list[i]=i;
bg_name_dirty[i]=0xFF;
}
bg_list_index=0x800;
/* reinitialize palette */
for(i = 0; i < 0x40; i += 1) color_update(i, *(uint16 *)&cram[i << 1]);
color_update(0x00, *(uint16 *)&cram[border << 1]);
}
/*--------------------------------------------------------------------------*/
/* DMA Operations */
/*--------------------------------------------------------------------------*/
/* Update DMA timings (this is call on start of DMA and then at the start of each scanline) */
void dma_update()
{
int dma_cycles = 0;
/* DMA timings table index */
int index = (4 * dma_type) + ((reg[12] & 1)*2);
if ((status&8) || !(reg[1] & 0x40)) index++;
/* DMA transfer rate */
int rate = dma_rates[index];
/* 68k cycles left */
int left_cycles = (line_m68k + m68cycles_per_line) - count_m68k;
if (left_cycles < 0) left_cycles = 0;
/* DMA bytes left */
int dma_bytes = (left_cycles * rate) / m68cycles_per_line;
/* determinate DMA length in CPU cycles */
if (dma_length < dma_bytes)
{
/* DMA will be finished during this line */
dma_cycles = (dma_length * m68cycles_per_line) / rate;
dma_length = 0;
}
else
{
/* DMA can not be finished until next scanline */
dma_cycles = left_cycles;
dma_length -= dma_bytes;
}
/* update 68k cycles counter */
if (dma_type < 2)
{
/* 68K COPY to V-RAM */
/* 68K is frozen during DMA operation */
count_m68k += dma_cycles;
}
else
{
/* VRAM Fill or VRAM Copy */
/* set DMA end cyles count */
dma_endCycles = count_m68k + dma_cycles;
/* set DMA Busy flag */
status |= 0x0002;
}
}
/* DMA Copy
Read byte from VRAM (source), write to VRAM (addr),
bump source and add r15 to addr.
- see how source addr is affected
(can it make high source byte inc?)
*/
static inline void dma_copy(void)
{
int name;
int length = (reg[20] << 8 | reg[19]) & 0xFFFF;
int source = (reg[22] << 8 | reg[21]) & 0xFFFF;
if (!length) length = 0x10000;
dma_type = 3;
dma_length = length;
dma_update();
/* proceed DMA */
do
{
vram[addr] = vram[source];
MARK_BG_DIRTY(addr);
source = (source + 1) & 0xFFFF;
addr += reg[15];
} while (--length);
/* update length & source address registers */
reg[19] = length & 0xFF;
reg[20] = (length >> 8) & 0xFF;
reg[21] = source & 0xFF; /* not sure */
reg[22] = (source >> 8) & 0xFF;
}
/* 68K Copy to VRAM, VSRAM or CRAM */
static inline void dma_vbus (void)
{
uint32 base, source = ((reg[23] & 0x7F) << 17 | reg[22] << 9 | reg[21] << 1) & 0xFFFFFE;
uint32 length = (reg[20] << 8 | reg[19]) & 0xFFFF;
uint32 temp;
if (!length) length = 0x10000;
base = source;
/* DMA timings */
dma_type = (code & 0x06) ? 1 : 0;
dma_length = length;
dma_update();
/* DMA source */
if ((source >> 17) == 0x50)
{
/* Z80 & I/O area */
do
{
/* Return $FFFF only when the Z80 isn't hogging the Z-bus.
(e.g. Z80 isn't reset and 68000 has the bus) */
if (source <= 0xa0ffff) temp = (zbusack ? *(uint16 *)(work_ram + (source & 0xffff)) : 0xffff);
/* The I/O chip and work RAM try to drive the data bus which results
in both values being combined in random ways when read.
We return the I/O chip values which seem to have precedence, */
else if (source <= 0xa1001f)
{
temp = io_read((source >> 1) & 0x0f);
temp = (temp << 8 | temp);
}
/* All remaining locations access work RAM */
else temp = *(uint16 *)(work_ram + (source & 0xffff));
source += 2;
source = ((base & 0xFE0000) | (source & 0x1FFFF));
data_write (temp);
}
while (--length);
}
else
{
/* SVP latency */
if (svp && (source < 0x400000))
{
source = (source - 2);
}
/* ROM & RAM */
do
{
temp = *(uint16 *)(m68k_memory_map[source>>16].base + (source & 0xffff));
source += 2;
source = ((base & 0xFE0000) | (source & 0x1FFFF));
data_write (temp);
}
while (--length);
}
/* update length & source address registers */
reg[19] = length & 0xFF;
reg[20] = (length >> 8) & 0xFF;
reg[21] = (source >> 1) & 0xFF;
reg[22] = (source >> 9) & 0xFF;
reg[23] = (reg[23] & 0x80) | ((source >> 17) & 0x7F);
}
/* VRAM FILL */
static inline void dma_fill(unsigned int data)
{
int name;
int length = (reg[20] << 8 | reg[19]) & 0xFFFF;
if (!length) length = 0x10000;
/* DMA timings */
dma_type = 2;
dma_length = length;
dma_update();
/* proceed DMA */
data_write(data);
/* write MSB */
data = (data >> 8) & 0xff;
/* detect internal SAT modification */
if ((addr & sat_base_mask) == satb)
{
do
{
/* update internal SAT (fix Battletech) */
WRITE_BYTE(sat, (addr & sat_addr_mask)^1, data);
WRITE_BYTE(vram, addr^1, data);
MARK_BG_DIRTY (addr);
addr += reg[15];
}
while (--length);
}
else
{
do
{
WRITE_BYTE(vram, addr^1, data);
MARK_BG_DIRTY (addr);
addr += reg[15];
}
while (--length);
}
/* update length register */
reg[19] = length & 0xFF;
reg[20] = (length >> 8) & 0xFF;
dmafill = 0;
}
/*--------------------------------------------------------------------------*/
/* FIFO emulation */
/*--------------------------------------------------------------------------*/
static inline void fifo_update()
{
if (fifo_write_cnt > 0)
{
/* update FIFO reads */
uint32 fifo_read = ((count_m68k - fifo_lastwrite) / fifo_latency);
if (fifo_read > 0)
{
fifo_write_cnt -= fifo_read;
if (fifo_write_cnt < 0) fifo_write_cnt = 0;
/* update cycle count */
fifo_lastwrite += fifo_read*fifo_latency;
}
}
}
/*--------------------------------------------------------------------------*/
/* Memory access functions */
/*--------------------------------------------------------------------------*/
static inline void data_write (unsigned int data)
{
switch (code & 0x0F)
{
case 0x01: /* VRAM */
/* Byte-swap data if A0 is set */
if (addr & 1) data = (data >> 8) | (data << 8);
/* Copy SAT data to the internal SAT */
if ((addr & sat_base_mask) == satb)
{
*(uint16 *) &sat[addr & sat_addr_mask & 0xFFFE] = data;
}
/* Only write unique data to VRAM */
if (data != *(uint16 *) &vram[addr & 0xFFFE])
{
/* Write data to VRAM */
*(uint16 *) &vram[addr & 0xFFFE] = data;
/* Update the pattern cache */
int name;
MARK_BG_DIRTY (addr);
}
break;
case 0x03: /* CRAM */
{
uint16 *p = (uint16 *) &cram[(addr & 0x7E)];
data = PACK_CRAM (data & 0x0EEE);
if (data != *p)
{
int index = (addr >> 1) & 0x3F;
*p = data;
color_update (index, *p);
color_update (0x00, *(uint16 *)&cram[border << 1]);
}
break;
}
case 0x05: /* VSRAM */
*(uint16 *) &vsram[(addr & 0x7E)] = data;
break;
}
/* Increment address register */
addr += reg[15];
}
void vdp_ctrl_w(unsigned int data)
{
if (pending == 0)
{
if ((data & 0xC000) == 0x8000)
{
/* VDP register write */
uint8 r = (data >> 8) & 0x1F;
uint8 d = data & 0xFF;
vdp_reg_w (r, d);
}
else pending = 1;
addr = ((addr_latch & 0xC000) | (data & 0x3FFF)) & 0xFFFF;
code = ((code & 0x3C) | ((data >> 14) & 0x03)) & 0x3F;
}
else
{
/* Clear pending flag */
pending = 0;
/* Update address and code registers */
addr = ((addr & 0x3FFF) | ((data & 3) << 14)) & 0xFFFF;
code = ((code & 0x03) | ((data >> 2) & 0x3C)) & 0x3F;
/* Save address bits A15 and A14 */
addr_latch = (addr & 0xC000);
/* DMA operation */
if ((code & 0x20) && (reg[1] & 0x10))
{
switch (reg[23] & 0xC0)
{
case 0x00: /* V bus to VDP DMA */
case 0x40: /* V bus to VDP DMA */
dma_vbus();
break;
case 0x80: /* VRAM fill */
dmafill = 1;
break;
case 0xC0: /* VRAM copy */
dma_copy();
break;
}
}
}
/* FIFO emulation:
---------------
HDISP is 256*10/7 = approx. 366 cycles (same for both modes)
this gives:
H32: 16 accesses --> 366/16 = 23 cycles per access
H40: 20 accesses --> 366/20 = 18 cycles per access
VRAM access are byte wide --> VRAM writes takes 2x CPU cycles
Memory access requires some additional cyles, the following values
seems to work fine (see Chaos Engine/Soldier of Fortune)
*/
fifo_latency = (reg[12] & 1) ? 27 : 30;
if ((code & 0x0F) == 0x01) fifo_latency = fifo_latency * 2;
}
/*
The reg[] array is updated at the *end* of this function, so the new
register data can be compared with the previous data.
*/
static inline void vdp_reg_w(unsigned int r, unsigned int d)
{
/* Check if Mode 4 (SMS mode) has been activated
According to official doc, VDP registers #11 to #23 can not be written unless bit2 in register #1 is set
Fix Captain Planet & Avengers (Alt version), Bass Master Classic Pro Edition (they incidentally activate Mode 4)
*/
if (!(reg[1] & 4) && (r > 10)) return;
switch(r)
{
case 0x00: /* CTRL #1 */
if (hint_pending && ((d&0x10) != (reg[0]&0x10)))
{
/* update IRQ status */
irq_status &= 0x20;
irq_status |= 0x10;
if (vint_pending && (reg[1] & 0x20)) irq_status |= 6;
else if (d & 0x10) irq_status |= 4;
}
break;
case 0x01: /* CTRL #2 */
if (vint_pending && ((d&0x20) != (reg[1]&0x20)))
{
/* update IRQ status */
irq_status &= 0x20;
irq_status |= 0x110;
if (d & 0x20) irq_status |= 6;
else if (hint_pending && (reg[0] & 0x10)) irq_status |= 4;
}
/* Check if the viewport height has actually been changed */
if((reg[1] & 8) != (d & 8))
{
/* Update the height of the viewport */
bitmap.viewport.h = (d & 8) ? 240 : 224;
if (config.overscan) bitmap.viewport.y = ((vdp_pal ? 288 : 240) - bitmap.viewport.h) / 2;
bitmap.viewport.changed = 1;
/* update VC table */
if (vdp_pal) vctab = (d & 8) ? vc_pal_240 : vc_pal_224;
}
/* DISPLAY switched ON/OFF during HBLANK */
if ((v_counter < bitmap.viewport.h) && ((d&0x40) != (reg[1]&0x40)))
{
if (count_m68k <= (hint_m68k + 120))
{
/* Redraw the current line :
- Legend of Galahad, Lemmings 2, Nigel Mansell's World Championship Racing (set display OFF)
- Deadly Moves aka Power Athlete (set display ON)
*/
reg[1] = d;
render_line(v_counter, 0);
}
}
break;
case 0x02: /* NTAB */
ntab = (d << 10) & 0xE000;
break;
case 0x03: /* NTWB */
ntwb = (d << 10) & 0xF800;
if(reg[12] & 1) ntwb &= 0xF000;
break;
case 0x04: /* NTBB */
ntbb = (d << 13) & 0xE000;
break;
case 0x05: /* SATB */
sat_base_mask = (reg[12] & 1) ? 0xFC00 : 0xFE00;
sat_addr_mask = (reg[12] & 1) ? 0x03FF : 0x01FF;
satb = (d << 9) & sat_base_mask;
break;
case 0x07: /* Border Color index */
/* Check if the border color has actually changed */
d &= 0x3F;
if(border != d)
{
/* Mark the border color as modified */
border = d;
color_update(0x00, *(uint16 *)&cram[(border << 1)]);
/* background color modified during HBLANK */
if ((v_counter < bitmap.viewport.h) && (count_m68k <= (line_m68k + 84)))
{
/* remap current line (see Road Rash I,II,III) */
reg[7] = d;
remap_buffer(v_counter,bitmap.viewport.w + 2*bitmap.viewport.x);
}
}
break;
case 0x0C:
/* Check if the viewport width has actually been changed */
if((reg[0x0C] & 1) != (d & 1))
{
/* Update the width of the viewport */
bitmap.viewport.w = (d & 1) ? 320 : 256;
if (config.overscan) bitmap.viewport.x = (d & 1) ? 16 : 12;
bitmap.viewport.changed = 1;
/* update HC table */
hctab = (d & 1) ? cycle2hc40 : cycle2hc32;
/* update clipping */
window_clip(d,reg[17]);
}
/* See if the S/TE mode bit has changed */
if((reg[0x0C] & 8) != (d & 8))
{
int i;
/* The following color update check this value */
reg[0x0C] = d;
/* Update colors */
for (i = 0; i < 0x40; i += 1) color_update (i, *(uint16 *) & cram[i << 1]);
color_update (0x00, *(uint16 *) & cram[border << 1]);
}
/* The following register updates check this value */
reg[0x0C] = d;
/* Update display-dependant registers */
vdp_reg_w(0x03, reg[0x03]);
vdp_reg_w(0x05, reg[0x05]);
break;
case 0x0D: /* HSCB */
hscb = (d << 10) & 0xFC00;
break;
case 0x10: /* Playfield size */
playfield_shift = shift_table[(d & 3)];
playfield_col_mask = col_mask_table[(d & 3)];
playfield_row_mask = row_mask_table[(d >> 4) & 3];
y_mask = y_mask_table[(d & 3)];
break;
case 0x11: /* update clipping */
window_clip(reg[12],d);
break;
}
/* Write new register value */
reg[r] = d;
}
/*
* Return VDP status
*
* Bits are
* 0 0:1 ntsc:pal
* 1 DMA Busy
* 2 During HBlank
* 3 During VBlank
* 4 Frame Interlace 0:even 1:odd
* 5 Sprite collision
* 6 Too many sprites per line
* 7 v interrupt occurred
* 8 Write FIFO full
* 9 Write FIFO empty
* 10 - 15 Next word on bus
*/
unsigned int vdp_ctrl_r(void)
{
/* update FIFO flags */
fifo_update();
if (fifo_write_cnt < 4)
{
status &= 0xFEFF;
if (fifo_write_cnt == 0) status |= 0x200;
}
else status ^= 0x200;
/* update DMA Busy flag */
if ((status & 2) && !dma_length && (count_m68k >= dma_endCycles))
{
status &= 0xFFFD;
}
unsigned int temp = status;
/* display OFF: VBLANK flag is set */
if (!(reg[1] & 0x40)) temp |= 0x8;
/* HBLANK flag (Sonic 3 and Sonic 2 "VS Modes", Lemmings 2) */
if ((count_m68k <= (line_m68k + 84)) || (count_m68k > (line_m68k + m68cycles_per_line))) temp |= 0x4;
/* clear pending flag */
pending = 0;
/* clear SPR/SCOL flags */
status &= 0xFF9F;
return (temp);
}
void vdp_data_w(unsigned int data)
{
/* Clear pending flag */
pending = 0;
if (dmafill)
{
dma_fill(data);
return;
}
/* update VDP FIFO (during HDISPLAY only) */
if (!(status&8) && (reg[1]&0x40))
{
fifo_update();
if (fifo_write_cnt == 0)
{
/* reset cycle counter */
fifo_lastwrite = count_m68k;
/* FIFO is not empty anymore */
status &= 0xFDFF;
}
/* increase write counter */
fifo_write_cnt ++;
/* is FIFO full ? */
if (fifo_write_cnt >= 4)
{
status |= 0x100;
/* VDP latency (Chaos Engine, Soldiers of Fortune, Double Clutch) */
if (fifo_write_cnt > 4) count_m68k = fifo_lastwrite + fifo_latency;
}
}
/* write data */
data_write(data);
}
unsigned int vdp_data_r(void)
{
uint16 temp = 0;
/* Clear pending flag */
pending = 0;
switch (code & 0x0F)
{
case 0x00: /* VRAM */
temp = *(uint16 *) & vram[(addr & 0xFFFE)];
break;
case 0x08: /* CRAM */
temp = *(uint16 *) & cram[(addr & 0x7E)];
temp = UNPACK_CRAM (temp);
break;
case 0x04: /* VSRAM */
temp = *(uint16 *) & vsram[(addr & 0x7E)];
break;
}
/* Increment address register */
addr += reg[15];
/* return data */
return (temp);
}
unsigned int vdp_hvc_r(void)
{
uint8 hc = (hc_latch & 0x100) ? (hc_latch & 0xFF) : hctab[count_m68k % m68cycles_per_line];
uint8 vc = vctab[v_counter];
/* interlace mode 2 */
if (im2_flag) vc = (vc << 1) | ((vc >> 7) & 1);
return ((vc << 8) | hc);
}
void vdp_test_w(unsigned int value)
{
#ifdef LOGERROR
error("Unused VDP Write 0x%x (%08x)\n", value, m68k_get_reg (NULL, M68K_REG_PC));
#endif
}
int vdp_int_ack_callback(int int_level)
{
/* VINT triggered ? */
if (irq_status&0x20)
{
vint_pending = 0;
status &= ~0x80; /* clear VINT flag */
}
else
{
hint_pending = 0;
}
/* update IRQ status */
irq_status = 0x10;
if (vint_pending && (reg[1] & 0x20)) irq_status |= 6;
else if (hint_pending && (reg[0] & 0x10)) irq_status |= 4;
return M68K_INT_ACK_AUTOVECTOR;
}
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