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Genesis-Plus-GX/core/system.c

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/***************************************************************************************
* Genesis Plus
* Virtual System emulation
*
* Support for 16-bit & 8-bit hardware modes
*
* Copyright (C) 1998-2003 Charles Mac Donald (original code)
* Copyright (C) 2007-2021 Eke-Eke (Genesis Plus GX)
*
* Redistribution and use of this code or any derivative works are permitted
* provided that the following conditions are met:
*
* - Redistributions may not be sold, nor may they be used in a commercial
* product or activity.
*
* - Redistributions that are modified from the original source must include the
* complete source code, including the source code for all components used by a
* binary built from the modified sources. However, as a special exception, the
* source code distributed need not include anything that is normally distributed
* (in either source or binary form) with the major components (compiler, kernel,
* and so on) of the operating system on which the executable runs, unless that
* component itself accompanies the executable.
*
* - Redistributions must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************************/
#include "shared.h"
#include "eq.h"
/* Global variables */
t_bitmap bitmap;
t_snd snd;
uint32 mcycles_vdp;
uint8 system_hw;
uint8 system_bios;
uint32 system_clock;
int16 SVP_cycles = 800;
static uint8 pause_b;
static EQSTATE eq[2];
static int16 llp,rrp;
/******************************************************************************************/
/* Audio subsystem */
/******************************************************************************************/
int audio_init(int samplerate, double framerate)
{
/* Shutdown first */
audio_shutdown();
/* Clear the sound data context */
memset(&snd, 0, sizeof (snd));
/* Initialize Blip Buffers */
snd.blips[0] = blip_new(samplerate / 10);
if (!snd.blips[0])
{
return -1;
}
/* Mega CD sound hardware */
if (system_hw == SYSTEM_MCD)
{
/* allocate blip buffers */
snd.blips[1] = blip_new(samplerate / 10);
snd.blips[2] = blip_new(samplerate / 10);
if (!snd.blips[1] || !snd.blips[2])
{
audio_shutdown();
return -1;
}
}
/* Initialize resampler internal rates */
audio_set_rate(samplerate, framerate);
/* Set audio enable flag */
snd.enabled = 1;
/* Reset audio */
audio_reset();
return (0);
}
void audio_set_rate(int samplerate, double framerate)
{
/* Number of M-cycles executed per second. */
/* All emulated chips are kept in sync by using a common oscillator (MCLOCK) */
/* */
/* The original console would run exactly 53693175 M-cycles per sec (53203424 for PAL), */
/* 3420 M-cycles per line and 262 (313 for PAL) lines per frame, which gives an exact */
/* framerate of 59.92 (49.70 for PAL) frames per second. */
/* */
/* Since audio samples are generated at the end of the frame, to prevent audio skipping */
/* or lag between emulated frames, number of samples rendered per frame must be set to */
/* output samplerate (number of samples played per second) divided by input framerate */
/* (number of frames emulated per seconds). */
/* */
/* On some systems, we may want to achieve 100% smooth video rendering by synchronizing */
/* frame emulation with VSYNC, which frequency is generally not exactly those values. */
/* In that case, input framerate (number of frames emulated per seconds) is the same as */
/* output framerate (number of frames rendered per seconds) by the host video hardware. */
/* */
/* When no framerate is specified, base clock is set to original master clock value. */
/* Otherwise, it is set to number of M-cycles emulated per line (fixed) multiplied by */
/* number of lines per frame (VDP mode specific) multiplied by input framerate. */
/* */
double mclk = framerate ? (MCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * framerate) : system_clock;
/* For maximal accuracy, sound chips are running at their original rate using common */
/* master clock timebase so they remain perfectly synchronized together, while still */
/* being synchronized with 68K and Z80 CPUs as well. Mixed sound chip output is then */
/* resampled to desired rate at the end of each frame, using Blip Buffer. */
blip_set_rates(snd.blips[0], mclk, samplerate);
/* Mega CD sound hardware enabled ? */
if (snd.blips[1] && snd.blips[2])
{
/* number of SCD master clocks run per second */
mclk = (mclk / system_clock) * SCD_CLOCK;
/* PCM core */
pcm_init(mclk, samplerate);
/* CDD core */
cdd_init(samplerate);
}
/* Reinitialize internal rates */
snd.sample_rate = samplerate;
snd.frame_rate = framerate;
}
void audio_reset(void)
{
int i;
/* Clear blip buffers */
for (i=0; i<3; i++)
{
if (snd.blips[i])
{
blip_clear(snd.blips[i]);
}
}
/* Low-Pass filter */
llp = 0;
rrp = 0;
/* 3 band EQ */
audio_set_equalizer();
}
void audio_set_equalizer(void)
{
init_3band_state(&eq[0],config.low_freq,config.high_freq,snd.sample_rate);
init_3band_state(&eq[1],config.low_freq,config.high_freq,snd.sample_rate);
eq[0].lg = eq[1].lg = (double)(config.lg) / 100.0;
eq[0].mg = eq[1].mg = (double)(config.mg) / 100.0;
eq[0].hg = eq[1].hg = (double)(config.hg) / 100.0;
}
void audio_shutdown(void)
{
int i;
/* Delete blip buffers */
for (i=0; i<3; i++)
{
blip_delete(snd.blips[i]);
snd.blips[i] = 0;
}
}
int audio_update(int16 *buffer)
{
/* run sound chips until end of frame */
int size = sound_update(mcycles_vdp);
/* Mega CD sound hardware enabled ? */
if (snd.blips[1] && snd.blips[2])
{
/* sync PCM chip with other sound chips */
pcm_update(size);
/* read CDDA samples */
cdd_read_audio(size);
#ifdef ALIGN_SND
/* return an aligned number of samples if required */
size &= ALIGN_SND;
#endif
/* resample & mix FM/PSG, PCM & CD-DA streams to output buffer */
blip_mix_samples(snd.blips[0], snd.blips[1], snd.blips[2], buffer, size);
}
else
{
#ifdef ALIGN_SND
/* return an aligned number of samples if required */
size &= ALIGN_SND;
#endif
/* resample FM/PSG mixed stream to output buffer */
blip_read_samples(snd.blips[0], buffer, size);
}
/* Audio filtering */
if (config.filter)
{
int samples = size;
int16 *out = buffer;
int32 l, r;
if (config.filter & 1)
{
/* single-pole low-pass filter (6 dB/octave) */
uint32 factora = config.lp_range;
uint32 factorb = 0x10000 - factora;
/* restore previous sample */
l = llp;
r = rrp;
do
{
/* apply low-pass filter */
l = l*factora + out[0]*factorb;
r = r*factora + out[1]*factorb;
/* 16.16 fixed point */
l >>= 16;
r >>= 16;
/* update sound buffer */
*out++ = l;
*out++ = r;
}
while (--samples);
/* save last samples for next frame */
llp = l;
rrp = r;
}
else if (config.filter & 2)
{
do
{
/* 3 Band EQ */
l = do_3band(&eq[0],out[0]);
r = do_3band(&eq[1],out[1]);
/* clipping (16-bit samples) */
if (l > 32767) l = 32767;
else if (l < -32768) l = -32768;
if (r > 32767) r = 32767;
else if (r < -32768) r = -32768;
/* update sound buffer */
*out++ = l;
*out++ = r;
}
while (--samples);
}
}
/* Mono output mixing */
if (config.mono)
{
int16 out;
int samples = size;
do
{
out = (buffer[0] + buffer[1]) / 2;
*buffer++ = out;
*buffer++ = out;
}
while (--samples);
}
#ifdef LOGSOUND
error("%d samples returned\n\n",size);
#endif
return size;
}
/****************************************************************
* Virtual System emulation
****************************************************************/
void system_init(void)
{
gen_init();
io_init();
vdp_init();
render_init();
sound_init();
}
void system_reset(void)
{
gen_reset(1);
io_reset();
render_reset();
vdp_reset();
sound_reset();
audio_reset();
}
void system_frame_gen(int do_skip)
{
/* line counters */
int start, end, line;
/* reset frame cycle counter */
mcycles_vdp = 0;
/* reset VDP FIFO */
fifo_write_cnt = 0;
fifo_slots = 0;
/* check if display setings have changed during previous frame */
if (bitmap.viewport.changed & 2)
{
/* interlaced modes */
int old_interlaced = interlaced;
interlaced = (reg[12] & 0x02) >> 1;
if (old_interlaced != interlaced)
{
/* double resolution mode */
im2_flag = ((reg[12] & 0x06) == 0x06);
/* reset field status flag */
odd_frame = interlaced;
/* video mode has changed */
bitmap.viewport.changed = 5;
/* update rendering mode */
if (reg[1] & 0x04)
{
if (im2_flag)
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_im2_vs : render_bg_m5_im2;
render_obj = (reg[12] & 0x08) ? render_obj_m5_im2_ste : render_obj_m5_im2;
}
else
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_vs : render_bg_m5;
render_obj = (reg[12] & 0x08) ? render_obj_m5_ste : render_obj_m5;
}
}
}
else
{
/* clear flag */
bitmap.viewport.changed &= ~2;
}
/* active screen height */
if (reg[1] & 0x04)
{
/* Mode 5 */
if (reg[1] & 0x08)
{
/* 240 active lines */
bitmap.viewport.h = 240;
bitmap.viewport.y = (config.overscan & 1) * 24 * vdp_pal;
}
else
{
/* 224 active lines */
bitmap.viewport.h = 224;
bitmap.viewport.y = (config.overscan & 1) * (8 + (24 * vdp_pal));
}
}
else
{
/* Mode 4 (192 active lines) */
bitmap.viewport.h = 192;
bitmap.viewport.y = (config.overscan & 1) * 24 * (vdp_pal + 1);
}
/* active screen width */
bitmap.viewport.w = 256 + ((reg[12] & 0x01) << 6);
/* check viewport changes */
if (bitmap.viewport.h != bitmap.viewport.oh)
{
bitmap.viewport.oh = bitmap.viewport.h;
bitmap.viewport.changed |= 1;
}
}
/* first line of overscan */
if (bitmap.viewport.y)
{
blank_line(bitmap.viewport.h, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* clear DMA Busy, FIFO FULL & field flags */
status &= 0xFEED;
/* set VBLANK & FIFO EMPTY flags */
status |= 0x0208;
/* check interlaced modes */
if (interlaced)
{
/* switch even/odd field flag */
odd_frame ^= 1;
status |= (odd_frame << 4);
}
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(0);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* level 4 interrupt */
m68k_update_irq(4);
}
}
/* refresh inputs just before VINT (Warriors of Eternal Sun) */
osd_input_update();
/* VDP always starts after VBLANK so VINT cannot occur on first frame after a VDP reset (verified on real hardware) */
if (v_counter != bitmap.viewport.h)
{
/* reinitialize VCounter */
v_counter = bitmap.viewport.h;
/* delay between VBLANK flag & Vertical Interrupt (Dracula, OutRunners, VR Troopers) */
m68k_run(788);
if (zstate == 1)
{
z80_run(788);
}
/* set VINT flag */
status |= 0x80;
/* Vertical Interrupt */
vint_pending = 0x20;
if (reg[1] & 0x20)
{
/* level 6 interrupt */
m68k_set_irq(6);
}
/* assert Z80 interrupt */
Z80.irq_state = ASSERT_LINE;
}
/* run 68k & Z80 until end of line */
m68k_run(MCYCLES_PER_LINE);
if (zstate == 1)
{
z80_run(MCYCLES_PER_LINE);
}
/* Z80 interrupt is cleared at the end of the line */
Z80.irq_state = CLEAR_LINE;
/* run SVP chip */
if (svp)
{
ssp1601_run(SVP_cycles);
}
/* update VDP cycle count */
mcycles_vdp = MCYCLES_PER_LINE;
/* initialize line count */
line = bitmap.viewport.h + 1;
/* initialize overscan area */
start = lines_per_frame - bitmap.viewport.y;
end = bitmap.viewport.h + bitmap.viewport.y;
/* Vertical Blanking */
do
{
/* update VCounter */
v_counter = line;
/* render overscan */
if ((line < end) || (line >= start))
{
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run 68k & Z80 until end of line */
m68k_run(mcycles_vdp + MCYCLES_PER_LINE);
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* run SVP chip */
if (svp)
{
ssp1601_run(SVP_cycles);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < (lines_per_frame - 1));
/* update VCounter */
v_counter = line;
/* last line of overscan */
if (bitmap.viewport.y)
{
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* reload H-Int counter */
h_counter = reg[10];
/* clear VBLANK flag */
status &= ~0x08;
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* parse first line of sprites */
if (reg[1] & 0x40)
{
parse_satb(-1);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run 68k & Z80 until end of line */
m68k_run(mcycles_vdp + MCYCLES_PER_LINE);
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* run SVP chip */
if (svp)
{
ssp1601_run(SVP_cycles);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
/* reset line count */
line = 0;
/* Active Display */
do
{
/* update VCounter */
v_counter = line;
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* render scanline */
if (!do_skip)
{
render_line(line);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* reload H-Int counter */
h_counter = reg[10];
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* level 4 interrupt */
m68k_update_irq(4);
}
}
else
{
/* decrement H-Int counter */
h_counter--;
}
/* run 68k & Z80 until end of line */
m68k_run(mcycles_vdp + MCYCLES_PER_LINE);
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* run SVP chip */
if (svp)
{
ssp1601_run(SVP_cycles);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < bitmap.viewport.h);
/* check viewport changes */
if (bitmap.viewport.w != bitmap.viewport.ow)
{
bitmap.viewport.ow = bitmap.viewport.w;
bitmap.viewport.changed |= 1;
}
/* adjust timings for next frame */
input_end_frame(mcycles_vdp);
m68k.cycles -= mcycles_vdp;
Z80.cycles -= mcycles_vdp;
}
void system_frame_scd(int do_skip)
{
/* line counters */
int start, end, line;
/* reset frame cycle counter */
mcycles_vdp = 0;
scd.cycles = 0;
/* reset VDP FIFO */
fifo_write_cnt = 0;
fifo_slots = 0;
/* check if display setings have changed during previous frame */
if (bitmap.viewport.changed & 2)
{
/* interlaced modes */
int old_interlaced = interlaced;
interlaced = (reg[12] & 0x02) >> 1;
if (old_interlaced != interlaced)
{
/* double resolution mode */
im2_flag = ((reg[12] & 0x06) == 0x06);
/* reset field status flag */
odd_frame = interlaced;
/* video mode has changed */
bitmap.viewport.changed = 5;
/* update rendering mode */
if (reg[1] & 0x04)
{
if (im2_flag)
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_im2_vs : render_bg_m5_im2;
render_obj = (reg[12] & 0x08) ? render_obj_m5_im2_ste : render_obj_m5_im2;
}
else
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_vs : render_bg_m5;
render_obj = (reg[12] & 0x08) ? render_obj_m5_ste : render_obj_m5;
}
}
}
else
{
/* clear flag */
bitmap.viewport.changed &= ~2;
}
/* active screen height */
if (reg[1] & 0x04)
{
/* Mode 5 */
if (reg[1] & 0x08)
{
/* 240 active lines */
bitmap.viewport.h = 240;
bitmap.viewport.y = (config.overscan & 1) * 24 * vdp_pal;
}
else
{
/* 224 active lines */
bitmap.viewport.h = 224;
bitmap.viewport.y = (config.overscan & 1) * (8 + (24 * vdp_pal));
}
}
else
{
/* Mode 4 (192 active lines) */
bitmap.viewport.h = 192;
bitmap.viewport.y = (config.overscan & 1) * 24 * (vdp_pal + 1);
}
/* active screen width */
bitmap.viewport.w = 256 + ((reg[12] & 0x01) << 6);
/* check viewport changes */
if (bitmap.viewport.h != bitmap.viewport.oh)
{
bitmap.viewport.oh = bitmap.viewport.h;
bitmap.viewport.changed |= 1;
}
}
/* first line of overscan */
if (bitmap.viewport.y)
{
blank_line(bitmap.viewport.h, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* clear DMA Busy, FIFO FULL & field flags */
status &= 0xFEED;
/* set VBLANK & FIFO EMPTY flags */
status |= 0x0208;
/* check interlaced modes */
if (interlaced)
{
/* switch even/odd field flag */
odd_frame ^= 1;
status |= (odd_frame << 4);
}
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(0);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* level 4 interrupt */
m68k_update_irq(4);
}
}
/* refresh inputs just before VINT */
osd_input_update();
/* VDP always starts after VBLANK so VINT cannot occur on first frame after a VDP reset (verified on real hardware) */
if (v_counter != bitmap.viewport.h)
{
/* reinitialize VCounter */
v_counter = bitmap.viewport.h;
/* delay between VBLANK flag & Vertical Interrupt (Dracula, OutRunners, VR Troopers) */
m68k_run(788);
if (zstate == 1)
{
z80_run(788);
}
/* set VINT flag */
status |= 0x80;
/* Vertical Interrupt */
vint_pending = 0x20;
if (reg[1] & 0x20)
{
/* level 6 interrupt */
m68k_set_irq(6);
}
/* assert Z80 interrupt */
Z80.irq_state = ASSERT_LINE;
}
/* run both 68k & CD hardware until end of line */
scd_update(MCYCLES_PER_LINE);
/* run Z80 until end of line */
if (zstate == 1)
{
z80_run(MCYCLES_PER_LINE);
}
/* Z80 interrupt is cleared at the end of the line */
Z80.irq_state = CLEAR_LINE;
/* update VDP cycle count */
mcycles_vdp = MCYCLES_PER_LINE;
/* initialize line count */
line = bitmap.viewport.h + 1;
/* initialize overscan area */
start = lines_per_frame - bitmap.viewport.y;
end = bitmap.viewport.h + bitmap.viewport.y;
/* Vertical Blanking */
do
{
/* update VCounter */
v_counter = line;
/* render overscan */
if ((line < end) || (line >= start))
{
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run both 68k & CD hardware until end of line */
scd_update(mcycles_vdp + MCYCLES_PER_LINE);
/* run Z80 until end of line */
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < (lines_per_frame - 1));
/* update VCounter */
v_counter = line;
/* last line of overscan */
if (bitmap.viewport.y)
{
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* reload H-Int counter */
h_counter = reg[10];
/* clear VBLANK flag */
status &= ~0x08;
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* parse first line of sprites */
if (reg[1] & 0x40)
{
parse_satb(-1);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run both 68k & CD hardware until end of line */
scd_update(mcycles_vdp + MCYCLES_PER_LINE);
/* run Z80 until end of line */
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
/* reset line count */
line = 0;
/* Active Display */
do
{
/* update VCounter */
v_counter = line;
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* render scanline */
if (!do_skip)
{
render_line(line);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* reload H-Int counter */
h_counter = reg[10];
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* level 4 interrupt */
m68k_update_irq(4);
}
}
else
{
/* decrement H-Int counter */
h_counter--;
}
/* run both 68k & CD hardware until end of line */
scd_update(mcycles_vdp + MCYCLES_PER_LINE);
/* run Z80 until end of line */
if (zstate == 1)
{
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
}
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < bitmap.viewport.h);
/* check viewport changes */
if (bitmap.viewport.w != bitmap.viewport.ow)
{
bitmap.viewport.ow = bitmap.viewport.w;
bitmap.viewport.changed |= 1;
}
/* adjust timings for next frame */
scd_end_frame(scd.cycles);
input_end_frame(mcycles_vdp);
m68k.cycles -= mcycles_vdp;
Z80.cycles -= mcycles_vdp;
}
void system_frame_sms(int do_skip)
{
/* line counter */
int start, end, line;
/* reset frame cycle count */
mcycles_vdp = 0;
/* reset VDP FIFO */
fifo_write_cnt = 0;
fifo_slots = 0;
/* check if display settings has changed during previous frame */
if (bitmap.viewport.changed & 2)
{
bitmap.viewport.changed &= ~2;
if (system_hw & SYSTEM_MD)
{
/* interlaced modes */
int old_interlaced = interlaced;
interlaced = (reg[12] & 0x02) >> 1;
if (old_interlaced != interlaced)
{
/* double resolution mode */
im2_flag = ((reg[12] & 0x06) == 0x06);
/* reset field status flag */
odd_frame = interlaced;
/* video mode has changed */
bitmap.viewport.changed = 5;
/* update rendering mode */
if (reg[1] & 0x04)
{
if (im2_flag)
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_im2_vs : render_bg_m5_im2;
render_obj = (reg[12] & 0x08) ? render_obj_m5_im2_ste : render_obj_m5_im2;
}
else
{
render_bg = (reg[11] & 0x04) ? render_bg_m5_vs : render_bg_m5;
render_obj = (reg[12] & 0x08) ? render_obj_m5_ste : render_obj_m5;
}
}
}
/* active screen height */
if (reg[1] & 0x04)
{
/* Mode 5 */
if (reg[1] & 0x08)
{
/* 240 active lines */
bitmap.viewport.h = 240;
bitmap.viewport.y = (config.overscan & 1) * 24 * vdp_pal;
}
else
{
/* 224 active lines */
bitmap.viewport.h = 224;
bitmap.viewport.y = (config.overscan & 1) * (8 + (24 * vdp_pal));
}
}
else
{
bitmap.viewport.h = 192;
bitmap.viewport.y = (config.overscan & 1) * 24 * (vdp_pal + 1);
}
}
else
{
/* check for VDP extended modes */
int mode = (reg[0] & 0x06) | (reg[1] & 0x18);
/* update active height */
if (mode == 0x0E)
{
bitmap.viewport.h = 240;
}
else if (mode == 0x16)
{
bitmap.viewport.h = 224;
}
else
{
bitmap.viewport.h = 192;
}
/* update vertical overscan */
if (config.overscan & 1)
{
bitmap.viewport.y = (240 + 48*vdp_pal - bitmap.viewport.h) >> 1;
}
else
{
if ((system_hw == SYSTEM_GG) && !config.gg_extra)
{
/* Display area reduced to 160x144 */
bitmap.viewport.y = (144 - bitmap.viewport.h) / 2;
}
else
{
bitmap.viewport.y = 0;
}
}
}
/* active screen width */
bitmap.viewport.w = 256 + ((reg[12] & 0x01) << 6);
/* check viewport changes */
if (bitmap.viewport.h != bitmap.viewport.oh)
{
bitmap.viewport.oh = bitmap.viewport.h;
bitmap.viewport.changed |= 1;
}
}
/* initialize VCounter */
v_counter = bitmap.viewport.h;
/* first line of overscan */
if (bitmap.viewport.y > 0)
{
blank_line(v_counter, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* Mega Drive VDP specific */
if (system_hw & SYSTEM_MD)
{
/* clear DMA Busy & field flags */
status &= 0xED;
/* set VBLANK flag */
status |= 0x08;
/* interlaced modes only */
if (interlaced)
{
/* switch even/odd field flag */
odd_frame ^= 1;
status |= (odd_frame << 4);
}
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(0);
}
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* Cycle-accurate HINT */
/* IRQ line is latched between instructions, during instruction last cycle. */
/* This means that if Z80 cycle count is exactly a multiple of MCYCLES_PER_LINE, */
/* interrupt should be triggered AFTER the next instruction. */
if ((Z80.cycles % MCYCLES_PER_LINE) == 0)
{
z80_run(Z80.cycles + 1);
}
/* Z80 interrupt */
Z80.irq_state = ASSERT_LINE;
}
}
/* refresh inputs just before VINT */
osd_input_update();
/* run Z80 until end of line */
z80_run(MCYCLES_PER_LINE);
/* make sure VINT flag was not read (then cleared) by last instruction */
if (v_counter == bitmap.viewport.h)
{
/* Set VINT flag */
status |= 0x80;
/* Vertical Interrupt */
vint_pending = 0x20;
if (reg[1] & 0x20)
{
Z80.irq_state = ASSERT_LINE;
}
}
/* update VDP cycle count */
mcycles_vdp = MCYCLES_PER_LINE;
/* initialize line count */
line = bitmap.viewport.h + 1;
/* initialize overscan area */
start = lines_per_frame - bitmap.viewport.y;
end = bitmap.viewport.h + bitmap.viewport.y;
/* Vertical Blanking */
do
{
/* update VCounter */
v_counter = line;
/* render overscan */
if ((line < end) || (line >= start))
{
/* Master System & Game Gear VDP specific */
if ((system_hw < SYSTEM_MD) && (line > (lines_per_frame - 16)))
{
/* Sprites are still processed during top border */
if (reg[1] & 0x40)
{
render_obj((line - lines_per_frame) & 1);
}
/* Sprites pre-processing occurs even when display is disabled */
parse_satb(line - lines_per_frame);
}
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run Z80 until end of line */
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < (lines_per_frame - 1));
/* update VCounter */
v_counter = line;
/* last line of overscan */
if (bitmap.viewport.y > 0)
{
/* Master System & Game Gear VDP specific */
if (system_hw < SYSTEM_MD)
{
/* Sprites are still processed during top border */
if (reg[1] & 0x40)
{
render_obj(1);
}
}
blank_line(line, -bitmap.viewport.x, bitmap.viewport.w + 2*bitmap.viewport.x);
}
/* reload H-Int counter */
h_counter = reg[10];
/* Detect pause button input (in Game Gear Mode, NMI is not generated) */
if (system_hw != SYSTEM_GG)
{
if (input.pad[0] & INPUT_START)
{
/* NMI is edge-triggered */
if (!pause_b)
{
pause_b = 1;
z80_set_nmi_line(ASSERT_LINE);
z80_set_nmi_line(CLEAR_LINE);
}
}
else
{
pause_b = 0;
}
}
/* 3-D glasses faking: skip rendering of left lens frame */
do_skip |= (work_ram[0x1ffb] & cart.special & HW_3D_GLASSES);
/* Mega Drive VDP specific */
if (system_hw & SYSTEM_MD)
{
/* clear VBLANK flag */
status &= ~0x08;
/* run VDP DMA */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* parse first line of sprites */
if (reg[1] & 0x40)
{
parse_satb(-1);
}
}
/* Master System & Game Gear VDP specific */
else
{
/* Sprites pre-processing occurs even when display is disabled */
parse_satb(-1);
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* run Z80 until end of line */
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
/* latch Vertical Scroll register */
vscroll = reg[9];
/* reset line count */
line = 0;
/* Active Display */
do
{
/* run VDP DMA (Mega Drive VDP specific) */
if (dma_length)
{
vdp_dma_update(mcycles_vdp);
}
/* make sure that line has not already been rendered */
if (v_counter != line)
{
/* update VCounter */
v_counter = line;
/* render scanline */
if (!do_skip)
{
render_line(line);
}
}
/* update 6-Buttons & Lightguns */
input_refresh();
/* H-Int counter */
if (h_counter == 0)
{
/* reload H-Int counter */
h_counter = reg[10];
/* Horizontal Interrupt is pending */
hint_pending = 0x10;
if (reg[0] & 0x10)
{
/* Cycle-accurate HINT */
/* IRQ line is latched between instructions, during instruction last cycle. */
/* This means that if Z80 cycle count is exactly a multiple of MCYCLES_PER_LINE, */
/* interrupt should be triggered AFTER the next instruction. */
if ((Z80.cycles % MCYCLES_PER_LINE) == 0)
{
z80_run(Z80.cycles + 1);
}
/* assert Z80 interrupt */
Z80.irq_state = ASSERT_LINE;
}
}
else
{
/* decrement H-Int counter */
h_counter--;
}
/* run Z80 until end of line */
z80_run(mcycles_vdp + MCYCLES_PER_LINE);
/* update VDP cycle count */
mcycles_vdp += MCYCLES_PER_LINE;
}
while (++line < bitmap.viewport.h);
/* check viewport changes */
if (bitmap.viewport.w != bitmap.viewport.ow)
{
bitmap.viewport.ow = bitmap.viewport.w;
bitmap.viewport.changed |= 1;
}
/* adjust timings for next frame */
input_end_frame(mcycles_vdp);
Z80.cycles -= mcycles_vdp;
}
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