diff options
Diffstat (limited to 'ym2612.c')
| -rw-r--r-- | ym2612.c | 69 |
1 files changed, 67 insertions, 2 deletions
@@ -19,6 +19,7 @@ #define OP_UPDATE_PERIOD 144 enum { + REG_LFO = 0x22, REG_TIMERA_HIGH = 0x24, REG_TIMERA_LOW, REG_TIMERB, @@ -86,6 +87,19 @@ uint16_t rate_table_base[] = { uint16_t rate_table[64*8]; +uint8_t lfo_timer_values[] = {108, 77, 71, 67, 62, 44, 8, 5}; +uint8_t lfo_pm_base[][8] = { + {0, 0, 0, 0, 0, 0, 0, 0}, + {0, 0, 0, 0, 4, 4, 4, 4}, + {0, 0, 0, 4, 4, 4, 8, 8}, + {0, 0, 4, 4, 8, 8, 0xc, 0xc}, + {0, 0, 4, 8, 8, 8, 0xc,0x10}, + {0, 0, 8, 0xc,0x10,0x10,0x14,0x18}, + {0, 0,0x10,0x18,0x20,0x20,0x28,0x30}, + {0, 0,0x20,0x30,0x40,0x40,0x50,0x60} +}; +int16_t lfo_pm_table[128 * 32 * 8]; + #define MAX_ENVELOPE 0xFFC #define YM_DIVIDER 2 #define CYCLE_NEVER 0xFFFFFFFF @@ -182,6 +196,24 @@ void ym_init(ym2612_context * context, uint32_t sample_rate, uint32_t master_clo rate_table[rate * 8 + cycle] = value; } } + //populate LFO PM table from small base table + //seems like there must be a better way to derive this + for (int freq = 0; freq < 128; freq++) { + for (int pms = 0; pms < 8; pms++) { + for (int step = 0; step < 32; step++) { + int16_t value = 0; + for (int bit = 0x40, shift = 0; bit > 0; bit >>= 1, shift++) { + if (freq & bit) { + value += lfo_pm_base[pms][(step & 0x8) ? 7-step & 7 : step & 7] >> shift; + } + } + if (step & 0x10) { + value = -value; + } + lfo_pm_table[freq * 256 + pms * 32 + step] = value; + } + } + } } } @@ -219,6 +251,17 @@ void ym_run(ym2612_context * context, uint32_t to_cycle) } } } + //Update LFO + if (context->lfo_enable) { + if (context->lfo_counter) { + context->lfo_counter--; + } else { + context->lfo_counter = lfo_timer_values[context->lfo_freq]; + context->lfo_am_step += 2; + context->lfo_am_step &= 0xFE; + context->lfo_pm_step = context->lfo_am_step / 8; + } + } //Update Envelope Generator if (!(context->current_op % 3)) { uint32_t env_cyc = context->env_counter; @@ -296,6 +339,17 @@ void ym_run(ym2612_context * context, uint32_t to_cycle) //TODO: Modulate phase by LFO if necessary uint16_t phase = operator->phase_counter >> 10 & 0x3FF; operator->phase_counter += operator->phase_inc; + if (chan->pms) { + //not entirely sure this will get the precision correct, but I'd like to avoid recalculating phase + //increment every update when LFO phase modulation is enabled + int16_t lfo_mod = lfo_pm_table[(chan->fnum & 0x7F0) * 16 + chan->pms + context->lfo_pm_step]; + if (operator->multiple) { + lfo_mod *= operator->multiple; + } else { + lfo_mod >>= 1; + } + operator->phase_counter += lfo_mod; + } int16_t mod = 0; switch (op % 4) { @@ -536,7 +590,18 @@ void ym_data_write(ym2612_context * context, uint8_t value) //Shared regs switch (context->selected_reg) { - //TODO: Test reg and LFO + //TODO: Test reg + case REG_LFO: + if ((value & 0x8) && !context->lfo_enable) { + printf("LFO Enabled, Freq: %d\n", value & 0x7); + } + context->lfo_enable = value & 0x8; + if (!context->lfo_enable) { + context->lfo_am_step = context->lfo_pm_step = 0; + } + context->lfo_freq = value & 0x7; + + break; case REG_TIMERA_HIGH: context->timer_a_load &= 0x3; context->timer_a_load |= value << 2; @@ -680,7 +745,7 @@ void ym_data_write(ym2612_context * context, uint8_t value) context->channels[channel].feedback = value >> 3 & 0x7; break; case REG_LR_AMS_PMS: - context->channels[channel].pms = value & 0x7; + context->channels[channel].pms = (value & 0x7) * 32; context->channels[channel].ams = value >> 4 & 0x3; context->channels[channel].lr = value & 0xC0; //printf("Write of %X to LR_AMS_PMS reg for channel %d\n", value, channel); |