mirror of
https://github.com/TomHarte/CLK.git
synced 2024-08-16 16:28:59 +00:00
292 lines
7.4 KiB
C++
292 lines
7.4 KiB
C++
//
|
|
// AY-3-8910.cpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 14/10/2016.
|
|
// Copyright © 2016 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#include "AY38910.hpp"
|
|
|
|
using namespace GI;
|
|
|
|
AY38910::AY38910() :
|
|
selected_register_(0),
|
|
tone_counters_{0, 0, 0}, tone_periods_{0, 0, 0}, tone_outputs_{0, 0, 0},
|
|
noise_shift_register_(0xffff), noise_period_(0), noise_counter_(0), noise_output_(0),
|
|
envelope_divider_(0), envelope_period_(0), envelope_position_(0),
|
|
master_divider_(0),
|
|
output_registers_{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
|
|
{
|
|
output_registers_[8] = output_registers_[9] = output_registers_[10] = 0;
|
|
|
|
// set up envelope lookup tables
|
|
for(int c = 0; c < 16; c++)
|
|
{
|
|
for(int p = 0; p < 32; p++)
|
|
{
|
|
switch(c)
|
|
{
|
|
case 0: case 1: case 2: case 3: case 9:
|
|
envelope_shapes_[c][p] = (p < 16) ? (p^0xf) : 0;
|
|
envelope_overflow_masks_[c] = 0x1f;
|
|
break;
|
|
case 4: case 5: case 6: case 7: case 15:
|
|
envelope_shapes_[c][p] = (p < 16) ? p : 0;
|
|
envelope_overflow_masks_[c] = 0x1f;
|
|
break;
|
|
|
|
case 8:
|
|
envelope_shapes_[c][p] = (p & 0xf) ^ 0xf;
|
|
envelope_overflow_masks_[c] = 0x00;
|
|
break;
|
|
case 12:
|
|
envelope_shapes_[c][p] = (p & 0xf);
|
|
envelope_overflow_masks_[c] = 0x00;
|
|
break;
|
|
|
|
case 10:
|
|
envelope_shapes_[c][p] = (p & 0xf) ^ ((p < 16) ? 0xf : 0x0);
|
|
envelope_overflow_masks_[c] = 0x00;
|
|
break;
|
|
case 14:
|
|
envelope_shapes_[c][p] = (p & 0xf) ^ ((p < 16) ? 0x0 : 0xf);
|
|
envelope_overflow_masks_[c] = 0x00;
|
|
break;
|
|
|
|
case 11:
|
|
envelope_shapes_[c][p] = (p < 16) ? (p^0xf) : 0xf;
|
|
envelope_overflow_masks_[c] = 0x1f;
|
|
break;
|
|
case 13:
|
|
envelope_shapes_[c][p] = (p < 16) ? p : 0xf;
|
|
envelope_overflow_masks_[c] = 0x1f;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// set up volume lookup table
|
|
float max_volume = 8192;
|
|
float root_two = sqrtf(2.0f);
|
|
for(int v = 0; v < 16; v++)
|
|
{
|
|
volumes_[v] = (int)(max_volume / powf(root_two, (float)(v ^ 0xf)));
|
|
}
|
|
volumes_[0] = 0;
|
|
}
|
|
|
|
void AY38910::set_clock_rate(double clock_rate)
|
|
{
|
|
set_input_rate((float)clock_rate);
|
|
}
|
|
|
|
void AY38910::get_samples(unsigned int number_of_samples, int16_t *target)
|
|
{
|
|
int c = 0;
|
|
while((master_divider_&7) && c < number_of_samples)
|
|
{
|
|
target[c] = output_volume_;
|
|
master_divider_++;
|
|
c++;
|
|
}
|
|
|
|
while(c < number_of_samples)
|
|
{
|
|
#define step_channel(c) \
|
|
if(tone_counters_[c]) tone_counters_[c]--;\
|
|
else\
|
|
{\
|
|
tone_outputs_[c] ^= 1;\
|
|
tone_counters_[c] = tone_periods_[c];\
|
|
}
|
|
|
|
// update the tone channels
|
|
step_channel(0);
|
|
step_channel(1);
|
|
step_channel(2);
|
|
|
|
#undef step_channel
|
|
|
|
// ... the noise generator. This recomputes the new bit repeatedly but harmlessly, only shifting
|
|
// it into the official 17 upon divider underflow.
|
|
if(noise_counter_) noise_counter_--;
|
|
else
|
|
{
|
|
noise_counter_ = noise_period_;
|
|
noise_output_ ^= noise_shift_register_&1;
|
|
noise_shift_register_ |= ((noise_shift_register_ ^ (noise_shift_register_ >> 3))&1) << 17;
|
|
noise_shift_register_ >>= 1;
|
|
}
|
|
|
|
// ... and the envelope generator. Table based for pattern lookup, with a 'refill' step — a way of
|
|
// implementing non-repeating patterns by locking them to table position 0x1f.
|
|
if(envelope_divider_) envelope_divider_--;
|
|
else
|
|
{
|
|
envelope_divider_ = envelope_period_;
|
|
envelope_position_ ++;
|
|
if(envelope_position_ == 32) envelope_position_ = envelope_overflow_masks_[output_registers_[13]];
|
|
}
|
|
|
|
evaluate_output_volume();
|
|
|
|
for(int ic = 0; ic < 8 && c < number_of_samples; ic++)
|
|
{
|
|
target[c] = output_volume_;
|
|
c++;
|
|
master_divider_++;
|
|
}
|
|
}
|
|
|
|
master_divider_ &= 7;
|
|
}
|
|
|
|
void AY38910::evaluate_output_volume()
|
|
{
|
|
int envelope_volume = envelope_shapes_[output_registers_[13]][envelope_position_];
|
|
|
|
// The output level for a channel is:
|
|
// 1 if neither tone nor noise is enabled;
|
|
// 0 if either tone or noise is enabled and its value is low.
|
|
// The tone/noise enable bits use inverse logic — 0 = on, 1 = off — permitting the OR logic below.
|
|
#define tone_level(c, tone_bit) (tone_outputs_[c] | (output_registers_[7] >> tone_bit))
|
|
#define noise_level(c, noise_bit) (noise_output_ | (output_registers_[7] >> noise_bit))
|
|
|
|
#define level(c, tone_bit, noise_bit) tone_level(c, tone_bit) & noise_level(c, noise_bit) & 1
|
|
const int channel_levels[3] = {
|
|
level(0, 0, 3),
|
|
level(1, 1, 4),
|
|
level(2, 2, 5),
|
|
};
|
|
#undef level
|
|
|
|
// Channel volume is a simple selection: if the bit at 0x10 is set, use the envelope volume; otherwise use the lower four bits
|
|
#define channel_volume(c) \
|
|
((output_registers_[c] >> 4)&1) * envelope_volume + (((output_registers_[c] >> 4)&1)^1) * (output_registers_[c]&0xf)
|
|
|
|
const int volumes[3] = {
|
|
channel_volume(8),
|
|
channel_volume(9),
|
|
channel_volume(10)
|
|
};
|
|
#undef channel_volume
|
|
|
|
// Mix additively.
|
|
output_volume_ = (int16_t)(
|
|
volumes_[volumes[0]] * channel_levels[0] +
|
|
volumes_[volumes[1]] * channel_levels[1] +
|
|
volumes_[volumes[2]] * channel_levels[2]
|
|
);
|
|
}
|
|
|
|
void AY38910::select_register(uint8_t r)
|
|
{
|
|
selected_register_ = r & 0xf;
|
|
}
|
|
|
|
void AY38910::set_register_value(uint8_t value)
|
|
{
|
|
registers_[selected_register_] = value;
|
|
if(selected_register_ < 14)
|
|
{
|
|
int selected_register = selected_register_;
|
|
enqueue([=] () {
|
|
uint8_t masked_value = value;
|
|
switch(selected_register)
|
|
{
|
|
case 0: case 2: case 4:
|
|
case 1: case 3: case 5:
|
|
{
|
|
int channel = selected_register >> 1;
|
|
|
|
if(selected_register & 1)
|
|
tone_periods_[channel] = (tone_periods_[channel] & 0xff) | (uint16_t)((value&0xf) << 8);
|
|
else
|
|
tone_periods_[channel] = (tone_periods_[channel] & ~0xff) | value;
|
|
tone_counters_[channel] = tone_periods_[channel];
|
|
}
|
|
break;
|
|
|
|
case 6:
|
|
noise_period_ = value & 0x1f;
|
|
noise_counter_ = noise_period_;
|
|
break;
|
|
|
|
case 11:
|
|
envelope_period_ = (envelope_period_ & ~0xff) | value;
|
|
envelope_divider_ = envelope_period_;
|
|
break;
|
|
|
|
case 12:
|
|
envelope_period_ = (envelope_period_ & 0xff) | (int)(value << 8);
|
|
envelope_divider_ = envelope_period_;
|
|
break;
|
|
|
|
case 13:
|
|
masked_value &= 0xf;
|
|
envelope_position_ = 0;
|
|
break;
|
|
}
|
|
output_registers_[selected_register] = masked_value;
|
|
evaluate_output_volume();
|
|
});
|
|
}
|
|
}
|
|
|
|
uint8_t AY38910::get_register_value()
|
|
{
|
|
// This table ensures that bits that aren't defined within the AY are returned as 1s
|
|
// when read. I can't find documentation on this and don't have a machine to test, so
|
|
// this is provisionally a guess. TODO: investigate.
|
|
const uint8_t register_masks[16] = {
|
|
0x00, 0xf0, 0x00, 0xf0, 0x00, 0xf0, 0xe0, 0x00,
|
|
0xe0, 0xe0, 0xe0, 0x00, 0x00, 0xf0, 0x00, 0x00
|
|
};
|
|
|
|
return registers_[selected_register_] | register_masks[selected_register_];
|
|
}
|
|
|
|
uint8_t AY38910::get_port_output(bool port_b)
|
|
{
|
|
return registers_[port_b ? 15 : 14];
|
|
}
|
|
|
|
void AY38910::set_data_input(uint8_t r)
|
|
{
|
|
data_input_ = r;
|
|
}
|
|
|
|
uint8_t AY38910::get_data_output()
|
|
{
|
|
return data_output_;
|
|
}
|
|
|
|
void AY38910::set_control_lines(ControlLines control_lines)
|
|
{
|
|
ControlState new_state;
|
|
switch((int)control_lines)
|
|
{
|
|
default: new_state = Inactive; break;
|
|
|
|
case (int)(BCDIR | BC2 | BC1):
|
|
case BCDIR:
|
|
case BC1: new_state = LatchAddress; break;
|
|
|
|
case (int)(BC2 | BC1): new_state = Read; break;
|
|
case (int)(BCDIR | BC2): new_state = Write; break;
|
|
}
|
|
|
|
if(new_state != control_state_)
|
|
{
|
|
control_state_ = new_state;
|
|
switch(new_state)
|
|
{
|
|
default: break;
|
|
case LatchAddress: select_register(data_input_); break;
|
|
case Write: set_register_value(data_input_); break;
|
|
case Read: data_output_ = get_register_value(); break;
|
|
}
|
|
}
|
|
}
|