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Added preliminary working sound to beezer. [Lord Nightmare]

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This commit is contained in:
Jonathan Gevaryahu 2011-01-21 07:54:12 +00:00
parent 21156f6869
commit 1d78049857
6 changed files with 614 additions and 19 deletions
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1
.gitattributes vendored
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@ -1321,6 +1321,7 @@ src/mame/audio/atarijsa.c svneol=native#text/plain
src/mame/audio/atarijsa.h svneol=native#text/plain
src/mame/audio/avalnche.c svneol=native#text/plain
src/mame/audio/aztarac.c svneol=native#text/plain
src/mame/audio/beezer.c svneol=native#text/plain
src/mame/audio/blockade.c svneol=native#text/plain
src/mame/audio/bsktball.c svneol=native#text/plain
src/mame/audio/bzone.c svneol=native#text/plain

578
src/mame/audio/beezer.c Normal file
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@ -0,0 +1,578 @@
/*************************************************************************
Beezer 6522+6840 audio hardware
driver based on exidy audio hardware which it shares some similarity to
Original driver by ? (Nicola or Aaron, I think)
Preliminary, partially functional driver by Jonathan Gevaryahu
AKA Lord Nightmare
TODO:
* The entire NOISE generator is just copied from exidy.c and is completely
wrong. It should be using an MM5837 self-clocked LFSR with taps on bits
16(0x10) and 13(0xD)
* The entire audio 6522 VIA isn't even HANDLED in this driver yet, hence
the sound channel provided by the VIA is completely missing! (it is
handled in /machine/beezer.c as via 1 at the moment)
* Related to above, the hookup of timer1 out (from pb7 of 6522) isn't done
which means selectively latched noise cannot work properly.
* Several inexplicable things on the schematic are not handled, such as the
'VCO' input for 6840 channel 2 external clock whose source does not appear
anywhere on the schematic, nor does it handle the 'DMOD DATA' and 'DMOD
CLR' outputs for some sort of digital modulator (perhaps an hc55516?)
from the VIA, which also does not appear anywhere on schematic.
The latter the VIA *DOES* seem to write something to, but it may be just
a silence waveform for 55516, alternating zeroes and ones.
* The volume dac ram values could be handled better, currently the MSB bit
is just thrown out; it should invert the waveform.
* The channel mixing is done additively at the moment rather than
emulating the original multiplexer, which is actually not that hard to do
* The 'FM OR AM' output of the audio via (pb1) appears to control some sort
of suppression or filtering change of the post-DAC amplifier when enabled,
only during the TIMER1 OUT time-slot of the multiplexer, see page 1B 3-3
of schematics. This will be a MESS to emulate since theres a lot of analog
crap involved.
* The /INT line and related logic of the 6840 is not emulated, and should
be hooked to the audio 6809
* Convert this to a modern device instead of a deprecated old style device
Notes on multiplexer:
The sound output is from a DAC76xx 8-bit dac; driving this dac is a pair
of 74ls670 4x4 register files wired up as four 8-bit words;
The four words are used as the volumes for four 1-bit channels by inversion
of the MSB of the 8 bit value.
The four channels are:
CNT1 CNT0
0 0 6522 pin 7 output (squarewave) NOT EMULATED YET; 'FM or AM'
affects this slot only
0 1 6840 channel 1 clocked by E1(int) OR by 6522 PB7-latched NOISE
1 0 6840 channel 2 clocked by E1(int) OR by "VCO" ext (Huh?)
1 1 6840 channel 3 clocked by E1(int) OR by channel 2-latched NOISE
The four slots determine which address is selected of the 8-bit words and
which source will XOR against the MSB of the 8-bit word before it goes
to the DAC (effectively making the 8-bit word be a 7-bit volume control
plus optional wave invert). The speed which cnt0 and cnt1 count at is
E1/16 or 62500Hz.
*************************************************************************/
#include "emu.h"
#include "machine/rescap.h"
#include "streams.h"
#include "cpu/m6809/m6809.h"
#include "includes/beezer.h"
/*************************************
*
* Constants
*
*************************************/
#define CRYSTAL_OSC (XTAL_12MHz)
#define SH6840_CLOCK (CRYSTAL_OSC / 12)
#define MULTIPLEX_FREQ (SH6840_CLOCK / 16)
/*************************************
*
* Local variables
*
*************************************/
/* 6840 variables */
struct sh6840_timer_channel
{
UINT8 cr;
UINT8 state;
UINT8 leftovers;
UINT16 timer;
UINT32 clocks;
UINT8 int_flag;
union
{
#ifdef LSB_FIRST
struct { UINT8 l, h; } b;
#else
struct { UINT8 h, l; } b;
#endif
UINT16 w;
} counter;
};
typedef struct _beezer_sound_state beezer_sound_state;
struct _beezer_sound_state
{
device_t *maincpu;
/* IRQ variable */
UINT8 ptm_irq_state;
struct sh6840_timer_channel sh6840_timer[3];
INT16 sh6840_volume[4];
UINT8 sh6840_MSB_latch;
UINT8 sh6840_LSB_latch;
UINT8 sh6840_LFSR_oldxor;
UINT32 sh6840_LFSR_0;
UINT32 sh6840_LFSR_1;
UINT32 sh6840_LFSR_2;
UINT32 sh6840_LFSR_3;
UINT32 sh6840_clocks_per_sample;
UINT32 sh6840_clock_count;
UINT32 sh6840_noiselatch1;
UINT32 sh6840_noiselatch3;
/* sound streaming variables */
sound_stream *stream;
double freq_to_step;
};
INLINE beezer_sound_state *get_safe_token(device_t *device)
{
assert(device != NULL);
assert(device->type() == BEEZER);
return (beezer_sound_state *)downcast<legacy_device_base *>(device)->token();
}
/*************************************
*
* Interrupt generation helper
*
*************************************/
/*static WRITE_LINE_DEVICE_HANDLER( update_irq_state )
{
beezer_sound_state *sndstate = get_safe_token(device);
cputag_set_input_line(device->machine, "audiocpu", M6809_IRQ_LINE, (sndstate->ptm_irq_state) ? ASSERT_LINE : CLEAR_LINE);
}*/
/*************************************
*
* 6840 clock counting helper
*
*************************************/
// need to set int_flag properly here
INLINE void sh6840_apply_clock(struct sh6840_timer_channel *t, int clocks)
{
/* dual 8-bit case */
if (t->cr & 0x04)
{
/* handle full decrements */
while (clocks > t->counter.b.l)
{
clocks -= t->counter.b.l + 1;
t->counter.b.l = t->timer;
/* decrement MSB */
if (!t->counter.b.h--)
{
t->state = 0;
t->counter.w = t->timer;
}
/* state goes high when MSB is 0 */
else if (!t->counter.b.h)
{
t->state = 1;
t->clocks++;
}
}
/* subtract off the remainder */
t->counter.b.l -= clocks;
}
/* 16-bit case */
else
{
/* handle full decrements */
while (clocks > t->counter.w)
{
clocks -= t->counter.w + 1;
t->state ^= 1;
t->clocks += t->state;
t->counter.w = t->timer;
}
/* subtract off the remainder */
t->counter.w -= clocks;
}
}
/*************************************
*
* Noise generation helper
*
*************************************/
// TODO: switch this to using the 17 bit lfsr of the MM5837 (bit 17 xor bit 14)
INLINE int sh6840_update_noise(beezer_sound_state *state, int clocks)
{
UINT32 newxor;
int noise_clocks = 0;
int i;
/* loop over clocks */
for (i = 0; i < clocks; i++)
{
/* shift the LFSR. its a LOOOONG LFSR, so we need
* four longs to hold it all!
* first we grab new sample, then shift the high bits,
* then the low ones; finally or in the result and see if we've
* had a 0->1 transition */
newxor = (state->sh6840_LFSR_3 ^ state->sh6840_LFSR_2) >> 31; /* high bits of 3 and 2 xored is new xor */
state->sh6840_LFSR_3 <<= 1;
state->sh6840_LFSR_3 |= state->sh6840_LFSR_2 >> 31;
state->sh6840_LFSR_2 <<= 1;
state->sh6840_LFSR_2 |= state->sh6840_LFSR_1 >> 31;
state->sh6840_LFSR_1 <<= 1;
state->sh6840_LFSR_1 |= state->sh6840_LFSR_0 >> 31;
state->sh6840_LFSR_0 <<= 1;
state->sh6840_LFSR_0 |= newxor ^ state->sh6840_LFSR_oldxor;
state->sh6840_LFSR_oldxor = newxor;
/*printf("LFSR: %4x, %4x, %4x, %4x\n", sh6840_LFSR_3, sh6840_LFSR_2, sh6840_LFSR_1, sh6840_LFSR_0);*/
/* if we clocked 0->1, that will serve as an external clock */
if ((state->sh6840_LFSR_2 & 0x03) == 0x01) /* tap is at 96th bit */
{
noise_clocks++;
}
}
return noise_clocks;
}
/*************************************
*
* 6840 state saving
*
*************************************/
static void sh6840_register_state_globals(device_t *device)
{
beezer_sound_state *state = get_safe_token(device);
state_save_register_device_item_array(device, 0, state->sh6840_volume);
state_save_register_device_item(device, 0, state->sh6840_MSB_latch);
state_save_register_device_item(device, 0, state->sh6840_LSB_latch);
state_save_register_device_item(device, 0, state->sh6840_LFSR_oldxor);
state_save_register_device_item(device, 0, state->sh6840_LFSR_0);
state_save_register_device_item(device, 0, state->sh6840_LFSR_1);
state_save_register_device_item(device, 0, state->sh6840_LFSR_2);
state_save_register_device_item(device, 0, state->sh6840_LFSR_3);
state_save_register_device_item(device, 0, state->sh6840_clock_count);
state_save_register_device_item(device, 0, state->sh6840_noiselatch1);
state_save_register_device_item(device, 0, state->sh6840_noiselatch3);
state_save_register_device_item(device, 0, state->sh6840_timer[0].cr);
state_save_register_device_item(device, 0, state->sh6840_timer[0].state);
state_save_register_device_item(device, 0, state->sh6840_timer[0].leftovers);
state_save_register_device_item(device, 0, state->sh6840_timer[0].timer);
state_save_register_device_item(device, 0, state->sh6840_timer[0].clocks);
state_save_register_device_item(device, 0, state->sh6840_timer[0].counter.w);
state_save_register_device_item(device, 0, state->sh6840_timer[1].cr);
state_save_register_device_item(device, 0, state->sh6840_timer[1].state);
state_save_register_device_item(device, 0, state->sh6840_timer[1].leftovers);
state_save_register_device_item(device, 0, state->sh6840_timer[1].timer);
state_save_register_device_item(device, 0, state->sh6840_timer[1].clocks);
state_save_register_device_item(device, 0, state->sh6840_timer[1].counter.w);
state_save_register_device_item(device, 0, state->sh6840_timer[2].cr);
state_save_register_device_item(device, 0, state->sh6840_timer[2].state);
state_save_register_device_item(device, 0, state->sh6840_timer[2].leftovers);
state_save_register_device_item(device, 0, state->sh6840_timer[2].timer);
state_save_register_device_item(device, 0, state->sh6840_timer[2].clocks);
state_save_register_device_item(device, 0, state->sh6840_timer[2].counter.w);
}
/*************************************
*
* Core sound generation
*
*************************************/
static STREAM_UPDATE( beezer_stream_update )
{
beezer_sound_state *state = get_safe_token(device);
struct sh6840_timer_channel *sh6840_timer = state->sh6840_timer;
/* hack to skip the expensive lfsr noise generation unless at least one of the 2 channels which actually depend on it are set to use it as a source */
int noisy = ((sh6840_timer[0].cr & sh6840_timer[2].cr & 0x02) == 0);
stream_sample_t *buffer = outputs[0];
/* loop over samples */
while (samples--)
{
struct sh6840_timer_channel *t;
int clocks_this_sample;
int clocks;
INT16 sample = 0;
/* determine how many 6840 clocks this sample */
state->sh6840_clock_count += state->sh6840_clocks_per_sample;
clocks_this_sample = state->sh6840_clock_count >> 24;
state->sh6840_clock_count &= (1 << 24) - 1;
/* skip if nothing enabled */
if ((sh6840_timer[0].cr & 0x01) == 0) // if we're not in reset...
{
int noise_clocks_this_sample = 0;
UINT32 chan1_clocks;
/* generate noise if configured to do so */
if (noisy != 0)
noise_clocks_this_sample = sh6840_update_noise(state, clocks_this_sample);
/* handle timer 0 if enabled */
t = &sh6840_timer[0];
clocks = (t->cr & 0x02) ? clocks_this_sample : noise_clocks_this_sample;
sh6840_apply_clock(t, clocks);
if (t->state && (t->cr & 0x80))
sample += (state->sh6840_volume[1]&0x7F);
else
sample -= (state->sh6840_volume[1]&0x7F);
/* handle timer 1 if enabled */
t = &sh6840_timer[1];
chan1_clocks = t->clocks;
clocks = (t->cr & 0x02) ? clocks_this_sample : noise_clocks_this_sample; // TODO: this is WRONG: channel 1 is clocked by a mystery "VCO CLOCK" signal if not set to E clock. it may not even be connected to anything!
sh6840_apply_clock(t, clocks);
if (t->state && (t->cr & 0x80))
sample += (state->sh6840_volume[2]&0x7F);
else
sample -= (state->sh6840_volume[2]&0x7F);
/* generate channel 1-clocked noise if configured to do so */
if (noisy != 0)
noise_clocks_this_sample = sh6840_update_noise(state, t->clocks - chan1_clocks);
/* handle timer 2 if enabled */
t = &sh6840_timer[2];
clocks = (t->cr & 0x02) ? clocks_this_sample : noise_clocks_this_sample;
/* prescale */
if (t->cr & 0x01)
{
clocks += t->leftovers;
t->leftovers = clocks % 8;
clocks /= 8;
}
sh6840_apply_clock(t, clocks);
if (t->state && (t->cr & 0x80))
sample += (state->sh6840_volume[3]&0x7F);
else
sample -= (state->sh6840_volume[3]&0x7F);
}
//sample += (state->sh6840_volume[0]&0x7F)*state->sh6840_noiselatch1;
/* stash */
*buffer++ = sample*64;
}
}
/*************************************
*
* Audio startup routines
*
*************************************/
static DEVICE_START( common_sh_start )
{
beezer_sound_state *state = get_safe_token(device);
int sample_rate = MULTIPLEX_FREQ;
state->sh6840_clocks_per_sample = (int)(((double)SH6840_CLOCK / (double)sample_rate) * (double)(1 << 24));
/* allocate the stream */
state->stream = stream_create(device, 0, 1, sample_rate, NULL, beezer_stream_update);
state->maincpu = device->machine->device("maincpu");
sh6840_register_state_globals(device);
}
static DEVICE_START( beezer_sound )
{
//beezer_sound_state *state = get_safe_token(device);
DEVICE_START_CALL(common_sh_start);
}
DEFINE_LEGACY_SOUND_DEVICE(BEEZER, beezer_sound);
/*************************************
*
* Audio reset routines
*
*************************************/
static DEVICE_RESET( common_sh_reset )
{
beezer_sound_state *state = get_safe_token(device);
/* 6840 */
memset(state->sh6840_timer, 0, sizeof(state->sh6840_timer));
state->sh6840_MSB_latch = 0;
state->sh6840_LSB_latch = 0;
state->sh6840_volume[0] = 0;
state->sh6840_volume[1] = 0;
state->sh6840_volume[2] = 0;
state->sh6840_clock_count = 0;
state->sh6840_noiselatch1 = 0;
state->sh6840_noiselatch3 = 0;
/* LFSR */
state->sh6840_LFSR_oldxor = 0;
state->sh6840_LFSR_0 = 0xffffffff;
state->sh6840_LFSR_1 = 0xffffffff;
state->sh6840_LFSR_2 = 0xffffffff;
state->sh6840_LFSR_3 = 0xffffffff;
}
static DEVICE_RESET( beezer_sound )
{
DEVICE_RESET_CALL(common_sh_reset);
}
DEVICE_GET_INFO( beezer_sound )
{
switch (state)
{
/* --- the following bits of info are returned as 64-bit signed integers --- */
case DEVINFO_INT_TOKEN_BYTES: info->i = sizeof(beezer_sound_state); break;
/* --- the following bits of info are returned as pointers to data or functions --- */
case DEVINFO_FCT_START: info->start = DEVICE_START_NAME(beezer_sound); break;
case DEVINFO_FCT_RESET: info->reset = DEVICE_RESET_NAME(beezer_sound); break;
/* --- the following bits of info are returned as NULL-terminated strings --- */
case DEVINFO_STR_NAME: strcpy(info->s, "beezer SFX"); break;
case DEVINFO_STR_SOURCE_FILE: strcpy(info->s, __FILE__); break;
}
}
/*************************************
*
* 6840 timer handlers
*
*************************************/
READ8_DEVICE_HANDLER( beezer_sh6840_r )
{
beezer_sound_state *state = get_safe_token(device);
/* force an update of the stream */
stream_update(state->stream);
switch (offset)
{
/* offset 0: Motorola datasheet says it isn't used, Hitachi datasheet says it reads as 0s always*/
case 0:
return 0;
/* offset 1 reads the status register: bits 2 1 0 correspond to ints on channels 2,1,0, and bit 7 is an 'OR' of bits 2,1,0 */
case 1:
logerror("%04X:beezer_sh6840_r - unexpected read, status register is TODO!\n", cpu_get_pc(state->maincpu));
return 0;
/* offsets 2,4,6 read channel 0,1,2 MSBs and latch the LSB*/
case 2: case 4: case 6:
state->sh6840_LSB_latch = state->sh6840_timer[((offset<<1)-1)].counter.b.l;
return state->sh6840_timer[((offset<<1)-1)].counter.b.h;
/* offsets 3,5,7 read the LSB latch*/
default: /* case 3,5,7 */
return state->sh6840_LSB_latch;
}
}
WRITE8_DEVICE_HANDLER( beezer_timer1_w )
{
beezer_sound_state *state = get_safe_token(device);
/* force an update of the stream */
stream_update(state->stream);
if (data) // really should be rising edge
state->sh6840_noiselatch1 = state->sh6840_noiselatch3 = state->sh6840_LFSR_oldxor;
}
WRITE8_DEVICE_HANDLER( beezer_sh6840_w )
{
beezer_sound_state *state = get_safe_token(device);
struct sh6840_timer_channel *sh6840_timer = state->sh6840_timer;
/* force an update of the stream */
stream_update(state->stream);
switch (offset)
{
/* offset 0 writes to either channel 0 control or channel 2 control */
case 0:
if (sh6840_timer[1].cr & 0x01)
sh6840_timer[0].cr = data;
else
sh6840_timer[2].cr = data;
/* only support mode 0 and 2 */
if (((data >> 3) & 5) != 0)
fprintf(stderr,"beezer_sh6840_w - channel %d configured for mode %d (write was %02x to offset 0)", (sh6840_timer[1].cr & 0x01) ? 0 : 2, (data >> 3) & 7, data);
break;
/* offset 1 writes to channel 1 control */
case 1:
sh6840_timer[1].cr = data;
/* only support mode 0 and 2 */
if (((data >> 3) & 5) != 0)
fprintf(stderr,"beezer_sh6840_w - channel 1 configured for mode %d (write was %02x to offset 1)", (data >> 3) & 7, data);
break;
/* offsets 2/4/6 write to the common MSB latch */
case 2:
case 4:
case 6:
state->sh6840_MSB_latch = data;
break;
/* offsets 3/5/7 write to the LSB controls */
case 3:
case 5:
case 7:
{
/* latch the timer value */
int ch = (offset - 3) / 2;
sh6840_timer[ch].timer = (state->sh6840_MSB_latch << 8) | (data & 0xff);
/* if CR4 is clear, the value is loaded immediately */
if (!(sh6840_timer[ch].cr & 0x10))
sh6840_timer[ch].counter.w = sh6840_timer[ch].timer;
break;
}
}
}
/*************************************
*
* External sound effect controls
*
*************************************/
WRITE8_DEVICE_HANDLER( beezer_sfxctrl_w )
{
beezer_sound_state *state = get_safe_token(device);
stream_update(state->stream);
state->sh6840_volume[offset] = data;
//fprintf(stderr,"dacram: write of %0x to slot %0x\n", data, offset);
}

23
src/mame/drivers/beezer.c
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@ -13,6 +13,8 @@
#include "sound/dac.h"
#include "includes/beezer.h"
extern const via6522_interface b_via_0_interface;
extern const via6522_interface b_via_1_interface;
static ADDRESS_MAP_START( main_map, ADDRESS_SPACE_PROGRAM, 8 )
AM_RANGE(0x0000, 0xbfff) AM_RAM AM_BASE_MEMBER(beezer_state, videoram)
@ -22,11 +24,14 @@ static ADDRESS_MAP_START( main_map, ADDRESS_SPACE_PROGRAM, 8 )
ADDRESS_MAP_END
static ADDRESS_MAP_START( sound_map, ADDRESS_SPACE_PROGRAM, 8 )
AM_RANGE(0x0000, 0x07ff) AM_RAM
// AM_RANGE(0x1000, 0x10ff) AM_READWRITE(beezer_6840_r, beezer_6840_w)
AM_RANGE(0x1800, 0x18ff) AM_DEVREADWRITE_MODERN("via6522_1", via6522_device, read, write)
// AM_RANGE(0x8000, 0x9fff) AM_WRITE(beezer_dac_w)
AM_RANGE(0xe000, 0xffff) AM_ROM
AM_RANGE(0x0000, 0x07ff) AM_RAM // RAM at 0D
AM_RANGE(0x0800, 0x0fff) AM_RAM // optional RAM at 2D (can be rom here instead)
AM_RANGE(0x1000, 0x1007) AM_MIRROR(0x07F8) AM_DEVREADWRITE("custom", beezer_sh6840_r, beezer_sh6840_w)
AM_RANGE(0x1800, 0x180F) AM_MIRROR(0x07F0) AM_DEVREADWRITE_MODERN("via6522_1", via6522_device, read, write)
AM_RANGE(0x8000, 0x8003) AM_MIRROR(0x1FFC) AM_DEVWRITE("custom", beezer_sfxctrl_w)
//AM_RANGE(0xa000, 0xbfff) AM_ROM // ROM at 2D (can be ram here instead), unpopulated
//AM_RANGE(0xc000, 0xdfff) AM_ROM // ROM at 4D, unpopulated
AM_RANGE(0xe000, 0xffff) AM_ROM // ROM at 6D
ADDRESS_MAP_END
@ -97,10 +102,10 @@ static MACHINE_CONFIG_START( beezer, beezer_state )
/* sound hardware */
MCFG_SPEAKER_STANDARD_MONO("mono")
MCFG_SOUND_ADD("dac", DAC, 0)
MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
//MCFG_SOUND_ADD("custom", BEEZER, 0)
//MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 0.50)
//MCFG_SOUND_ADD("dac", DAC, 0)
//MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
MCFG_SOUND_ADD("custom", BEEZER, 0)
MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.00)
/* via */
MCFG_VIA6522_ADD("via6522_0", 0, b_via_0_interface)

11
src/mame/includes/beezer.h
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@ -10,12 +10,19 @@ public:
/*----------- defined in machine/beezer.c -----------*/
extern const via6522_interface b_via_0_interface;
extern const via6522_interface b_via_1_interface;
//extern const via6522_interface b_via_0_interface;
//extern const via6522_interface b_via_1_interface;
DRIVER_INIT( beezer );
WRITE8_HANDLER( beezer_bankswitch_w );
/*----------- defined in audio/beezer.c -----------*/
DECLARE_LEGACY_SOUND_DEVICE(BEEZER, beezer_sound);
READ8_DEVICE_HANDLER( beezer_sh6840_r );
WRITE8_DEVICE_HANDLER( beezer_sh6840_w );
WRITE8_DEVICE_HANDLER( beezer_sfxctrl_w );
/*----------- defined in video/beezer.c -----------*/

19
src/mame/machine/beezer.c
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@ -3,6 +3,9 @@
#include "machine/6522via.h"
#include "includes/beezer.h"
extern const via6522_interface b_via_0_interface;
extern const via6522_interface b_via_1_interface;
static int pbus;
static int banklatch;
@ -54,14 +57,14 @@ const via6522_interface b_via_0_interface =
port A:
bits 7-0: input/output: pbus
port B:
bit 7: output?: TIMER1 OUT (used to gate NOISE (see below) to clock channel 1 of 6840, plus acts as channel 0 by itself)
bit 7: output: TIMER1 OUT (used to gate NOISE (see below) to clock channel 1 of 6840, plus acts as channel 0 by itself)
bit 6: input: NOISE (from mn5837 14-bit LFSR, which also connects to clock above)
bit 5: N/C
bit 4: input: FMSEL1 (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 3: input: FMSEL0 (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 2: input: AM (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 1: input: FM or AM (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 0: input: DMOD DISABLE (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 5: output?: N/C
bit 4: output?: FMSEL1 (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 3: output?: FMSEL0 (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 2: output?: AM (does not appear elsewhere on schematics! what does this do? needs tracing)
bit 1: output: FM or AM (appears to control some sort of suppression or filtering change of the post-DAC amplifier when enabled, only during the TIMER1 OUT time-slot of the multiplexer, see page 1B 3-3 of schematics)
bit 0: output?: DMOD DISABLE (does not appear elsewhere on schematics! what does this do? needs tracing)
port C:
CA1: AHS2 from via 0 (are these two switched?)
CA2: AHS1 from via 0 "
@ -137,7 +140,7 @@ static READ8_DEVICE_HANDLER( b_via_1_pa_r )
static READ8_DEVICE_HANDLER( b_via_1_pb_r )
{
return 0xff; // TODO: sound readbacks go here
return 0x1F | (device->machine->rand()&0x40); // bit 6 is NOISE input from MM5837 17-bit LFSR
}
static WRITE8_DEVICE_HANDLER( b_via_1_pa_w )

1
src/mame/mame.mak
View File

@ -1428,6 +1428,7 @@ $(MAMEOBJ)/toaplan.a: \
$(MAMEOBJ)/tong.a: \
$(DRIVERS)/beezer.o $(MACHINE)/beezer.o $(VIDEO)/beezer.o \
$(AUDIO)/beezer.o \
$(MAMEOBJ)/unico.a: \
$(DRIVERS)/drgnmst.o $(VIDEO)/drgnmst.o \