/*****************************************************************************/ /* */ /* Module: POKEY Chip Simulator, V1.1 */ /* Purpose: To emulate the sound generation hardware of the Atari POKEY chip. */ /* Author: Ron Fries */ /* Date: September 22, 1996 */ /* */ /*****************************************************************************/ /* */ /* License Information and Copyright Notice */ /* ======================================== */ /* */ /* PokeySound is Copyright(c) 1996 by Ron Fries */ /* */ /* This library is free software; you can redistribute it and/or modify it */ /* under the terms of version 2 of the GNU Library General Public License */ /* as published by the Free Software Foundation. */ /* */ /* This library 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 Library */ /* General Public License for more details. */ /* To obtain a copy of the GNU Library General Public License, write to the */ /* Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* */ /* Any permitted reproduction of these routines, in whole or in part, must */ /* bear this legend. */ /* */ /*****************************************************************************/ #include #include #include #include "pokey11.h" /* CONSTANT DEFINITIONS */ /* definitions for AUDCx (D201, D203, D205, D207) */ #define NOTPOLY5 0x80 /* selects POLY5 or direct CLOCK */ #define POLY4 0x40 /* selects POLY4 or POLY17 */ #define PURE 0x20 /* selects POLY4/17 or PURE tone */ #define VOL_ONLY 0x10 /* selects VOLUME OUTPUT ONLY */ #define VOLUME_MASK 0x0f /* volume mask */ /* definitions for AUDCTL (D208) */ #define POLY9 0x80 /* selects POLY9 or POLY17 */ #define CH1_179 0x40 /* selects 1.78979 MHz for Ch 1 */ #define CH3_179 0x20 /* selects 1.78979 MHz for Ch 3 */ #define CH1_CH2 0x10 /* clocks channel 1 w/channel 2 */ #define CH3_CH4 0x08 /* clocks channel 3 w/channel 4 */ #define CH1_FILTER 0x04 /* selects channel 1 high pass filter */ #define CH2_FILTER 0x02 /* selects channel 2 high pass filter */ #define CLOCK_15 0x01 /* selects 15.6999kHz or 63.9210kHz */ #define AUDF1_C 0xd200 #define AUDC1_C 0xd201 #define AUDF2_C 0xd202 #define AUDC2_C 0xd203 #define AUDF3_C 0xd204 #define AUDC3_C 0xd205 #define AUDF4_C 0xd206 #define AUDC4_C 0xd207 #define AUDCTL_C 0xd208 /* for accuracy, the 64kHz and 15kHz clocks are exact divisions of the 1.79MHz clock */ #define DIV_64 28 /* divisor for 1.79MHz clock to 64 kHz */ #define DIV_15 114 /* divisor for 1.79MHz clock to 15 kHz */ /* the size (in entries) of the 4 polynomial tables */ #define POLY4_SIZE 0x000f #define POLY5_SIZE 0x001f #define POLY9_SIZE 0x01ff #ifdef COMP16 /* if 16-bit compiler */ #define POLY17_SIZE 0x00007fffL /* reduced to 15 bits for simplicity */ #else /* */ #define POLY17_SIZE 0x0001ffffL /* else use the full 17 bits */ #endif /* */ /* channel definitions */ #define CHAN1 0 #define CHAN2 1 #define CHAN3 2 #define CHAN4 3 #define SAMPLE 4 #define FALSE 0 #define TRUE 1 /* GLOBAL VARIABLE DEFINITIONS */ /* structures to hold the 9 pokey control bytes */ static uint8 AUDF[4]; /* AUDFx (D200, D202, D204, D206) */ static uint8 AUDC[4]; /* AUDCx (D201, D203, D205, D207) */ static uint8 AUDCTL; /* AUDCTL (D208) */ static uint8 Outbit[4]; /* current state of the output (high or low) */ static uint8 Outvol[4]; /* last output volume for each channel */ /* Initialze the bit patterns for the polynomials. */ /* The 4bit and 5bit patterns are the identical ones used in the pokey chip. */ /* Though the patterns could be packed with 8 bits per byte, using only a */ /* single bit per byte keeps the math simple, which is important for */ /* efficient processing. */ static uint8 bit4[POLY4_SIZE] = {1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0}; static uint8 bit5[POLY5_SIZE] = {0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1}; static uint8 bit17[POLY17_SIZE]; /* Rather than have a table with 131071 */ /* entries, I use a random number generator. */ /* It shouldn't make much difference since */ /* the pattern rarely repeats anyway. */ static uint32 Poly17_size; /* global for the poly 17 size, since it can */ /* be changed from 17 bit to 9 bit */ static uint32 Poly_adjust; /* the amount that the polynomial will need */ /* to be adjusted to process the next bit */ static uint32 P4 = 0, /* Global position pointer for the 4-bit POLY array */ P5 = 0, /* Global position pointer for the 5-bit POLY array */ P17 = 0; /* Global position pointer for the 17-bit POLY array */ static uint32 Div_n_cnt[4], /* Divide by n counter. one for each channel */ Div_n_max[4]; /* Divide by n maximum, one for each channel */ static uint32 Samp_n_max, /* Sample max. For accuracy, it is *256 */ Samp_n_cnt[2]; /* Sample cnt. */ static uint32 Base_mult; /* selects either 64Khz or 15Khz clock mult */ /*****************************************************************************/ /* In my routines, I treat the sample output as another divide by N counter */ /* For better accuracy, the Samp_n_cnt has a fixed binary decimal point */ /* which has 8 binary digits to the right of the decimal point. I use a two */ /* byte array to give me a minimum of 40 bits, and then use pointer math to */ /* reference either the 24.8 whole/fraction combination or the 32-bit whole */ /* only number. This is mainly used to keep the math simple for */ /* optimization. See below: */ /* */ /* xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx | xxxxxxxx xxxxxxxx xxxxxxxx.xxxxxxxx */ /* unused unused unused whole whole whole whole fraction */ /* */ /* Samp_n_cnt[0] gives me a 32-bit int 24 whole bits with 8 fractional bits, */ /* while (uint32 *)((uint8 *)(&Samp_n_cnt[0])+1) gives me the 32-bit whole */ /* number only. */ /*****************************************************************************/ /*****************************************************************************/ /* Module: Pokey_sound_init() */ /* Purpose: to handle the power-up initialization functions */ /* these functions should only be executed on a cold-restart */ /* */ /* Author: Ron Fries */ /* Date: September 22, 1996 */ /* */ /* Inputs: freq17 - the value for the '1.79MHz' Pokey audio clock */ /* playback_freq - the playback frequency in samples per second */ /* */ /* Outputs: Adjusts local globals - no return value */ /* */ /*****************************************************************************/ void Pokey_sound_init(uint32 freq17, uint16 playback_freq) { uint8 chan; int32 n; /* fill the 17bit polynomial with random bits */ for (n = 0; n < POLY17_SIZE; n++) { bit17[n] = rand() & 0x01; /* fill poly 17 with random bits */ } /* start all of the polynomial counters at zero */ Poly_adjust = 0; P4 = 0; P5 = 0; P17 = 0; /* calculate the sample 'divide by N' value based on the playback freq. */ Samp_n_max = ((uint32) freq17 << 8) / playback_freq; Samp_n_cnt[0] = 0; /* initialize all bits of the sample */ Samp_n_cnt[1] = 0; /* 'divide by N' counter */ Poly17_size = POLY17_SIZE; for (chan = CHAN1; chan <= CHAN4; chan++) { Outvol[chan] = 0; Outbit[chan] = 0; Div_n_cnt[chan] = 0; Div_n_max[chan] = 0x7fffffffL; AUDC[chan] = 0; AUDF[chan] = 0; } AUDCTL = 0; Base_mult = DIV_64; } /*****************************************************************************/ /* Module: Update_pokey_sound() */ /* Purpose: To process the latest control values stored in the AUDF, AUDC, */ /* and AUDCTL registers. It pre-calculates as much information as */ /* possible for better performance. This routine has not been */ /* optimized. */ /* */ /* Author: Ron Fries */ /* Date: September 22, 1996 */ /* */ /* Inputs: addr - the address of the parameter to be changed */ /* val - the new value to be placed in the specified address */ /* */ /* Outputs: Adjusts local globals - no return value */ /* */ /*****************************************************************************/ void Update_pokey_sound(uint16 addr, uint8 val) { uint32 new_val = 0; uint8 chan; uint8 chan_mask; /* determine which address was changed */ switch (addr) { case AUDF1_C: AUDF[CHAN1] = val; chan_mask = 1 << CHAN1; if (AUDCTL & CH1_CH2) /* if ch 1&2 tied together */ chan_mask |= 1 << CHAN2; /* then also change on ch2 */ break; case AUDC1_C: AUDC[CHAN1] = val; chan_mask = 1 << CHAN1; break; case AUDF2_C: AUDF[CHAN2] = val; chan_mask = 1 << CHAN2; break; case AUDC2_C: AUDC[CHAN2] = val; chan_mask = 1 << CHAN2; break; case AUDF3_C: AUDF[CHAN3] = val; chan_mask = 1 << CHAN3; if (AUDCTL & CH3_CH4) /* if ch 3&4 tied together */ chan_mask |= 1 << CHAN4; /* then also change on ch4 */ break; case AUDC3_C: AUDC[CHAN3] = val; chan_mask = 1 << CHAN3; break; case AUDF4_C: AUDF[CHAN4] = val; chan_mask = 1 << CHAN4; break; case AUDC4_C: AUDC[CHAN4] = val; chan_mask = 1 << CHAN4; break; case AUDCTL_C: AUDCTL = val; chan_mask = 15; /* all channels */ /* set poly17 counter to 9- or 17-bit */ if (AUDCTL & POLY9) Poly17_size = POLY9_SIZE; else Poly17_size = POLY17_SIZE; /* determine the base multiplier for the 'div by n' calculations */ if (AUDCTL & CLOCK_15) Base_mult = DIV_15; else Base_mult = DIV_64; break; default: chan_mask = 0; break; } /************************************************************/ /* As defined in the manual, the exact Div_n_cnt values are */ /* different depending on the frequency and resolution: */ /* 64 kHz or 15 kHz - AUDF + 1 */ /* 1 MHz, 8-bit - AUDF + 4 */ /* 1 MHz, 16-bit - AUDF[CHAN1]+256*AUDF[CHAN2] + 7 */ /************************************************************/ /* only reset the channels that have changed */ if (chan_mask & (1 << CHAN1)) { /* process channel 1 frequency */ if (AUDCTL & CH1_179) new_val = AUDF[CHAN1] + 4; else new_val = (AUDF[CHAN1] + 1) * Base_mult; if (new_val != Div_n_max[CHAN1]) { Div_n_max[CHAN1] = new_val; Div_n_cnt[CHAN1] = 0; } } if (chan_mask & (1 << CHAN2)) { /* process channel 2 frequency */ if (AUDCTL & CH1_CH2) if (AUDCTL & CH1_179) new_val = AUDF[CHAN2] * 256 + AUDF[CHAN1] + 7; else new_val = (AUDF[CHAN2] * 256 + AUDF[CHAN1] + 1) * Base_mult; else new_val = (AUDF[CHAN2] + 1) * Base_mult; if (new_val != Div_n_max[CHAN2]) { Div_n_max[CHAN2] = new_val; Div_n_cnt[CHAN2] = 0; } } if (chan_mask & (1 << CHAN3)) { /* process channel 3 frequency */ if (AUDCTL & CH3_179) new_val = AUDF[CHAN3] + 4; else new_val = (AUDF[CHAN3] + 1) * Base_mult; if (new_val != Div_n_max[CHAN3]) { Div_n_max[CHAN3] = new_val; Div_n_cnt[CHAN3] = 0; } } if (chan_mask & (1 << CHAN4)) { /* process channel 4 frequency */ if (AUDCTL & CH3_CH4) if (AUDCTL & CH3_179) new_val = AUDF[CHAN4] * 256 + AUDF[CHAN3] + 7; else new_val = (AUDF[CHAN4] * 256 + AUDF[CHAN3] + 1) * Base_mult; else new_val = (AUDF[CHAN4] + 1) * Base_mult; if (new_val != Div_n_max[CHAN4]) { Div_n_max[CHAN4] = new_val; Div_n_cnt[CHAN4] = 0; } } /* if channel is volume only, set current output */ for (chan = CHAN1; chan <= CHAN4; chan++) { if (chan_mask & (1 << chan)) { /* I've disabled any frequencies that exceed the sampling frequency. There isn't much point in processing frequencies that the hardware can't reproduce. I've also disabled processing if the volume is zero. */ /* if the channel is volume only */ /* or the channel is off (volume == 0) */ /* or the channel freq is greater than the playback freq */ if ((AUDC[chan] & VOL_ONLY) || ((AUDC[chan] & VOLUME_MASK) == 0) || (Div_n_max[chan] < (Samp_n_max >> 8))) { /* then set the channel to the selected volume */ Outvol[chan] = AUDC[chan] & VOLUME_MASK; /* and set channel freq to max to reduce processing */ Div_n_max[chan] = 0x7fffffffL; } } } } /*****************************************************************************/ /* Module: Pokey_process_2() */ /* Purpose: To fill the output buffer with the sound output based on the */ /* pokey chip parameters. This routine has not been optimized. */ /* Though it is not used by the program, I've left it for reference. */ /* */ /* Author: Ron Fries */ /* Date: September 22, 1996 */ /* */ /* Inputs: *buffer - pointer to the buffer where the audio output will */ /* be placed */ /* n - size of the playback buffer */ /* */ /* Outputs: the buffer will be filled with n bytes of audio - no return val */ /* */ /*****************************************************************************/ void Pokey_process_2(register unsigned char *buffer, register uint16 n) { register uint32 *samp_cnt_w_ptr; register uint32 event_min; register uint8 next_event; register uint8 cur_val; register uint8 chan; /* set a pointer to the whole portion of the samp_n_cnt */ samp_cnt_w_ptr = (uint32 *) ((uint8 *) (&Samp_n_cnt[0]) + 1); /* loop until the buffer is filled */ while (n) { /* Normally the routine would simply decrement the 'div by N' */ /* counters and react when they reach zero. Since we normally */ /* won't be processing except once every 80 or so counts, */ /* I've optimized by finding the smallest count and then */ /* 'accelerated' time by adjusting all pointers by that amount. */ /* find next smallest event (either sample or chan 1-4) */ next_event = SAMPLE; event_min = *samp_cnt_w_ptr; for (chan = CHAN1; chan <= CHAN4; chan++) { if (Div_n_cnt[chan] <= event_min) { event_min = Div_n_cnt[chan]; next_event = chan; } } /* decrement all counters by the smallest count found */ for (chan = CHAN1; chan <= CHAN4; chan++) { Div_n_cnt[chan] -= event_min; } *samp_cnt_w_ptr -= event_min; /* since the polynomials require a mod (%) function which is division, I don't adjust the polynomials on the SAMPLE events, only the CHAN events. I have to keep track of the change, though. */ Poly_adjust += event_min; /* if the next event is a channel change */ if (next_event != SAMPLE) { /* shift the polynomial counters */ P4 = (P4 + Poly_adjust) % POLY4_SIZE; P5 = (P5 + Poly_adjust) % POLY5_SIZE; P17 = (P17 + Poly_adjust) % Poly17_size; /* reset the polynomial adjust counter to zero */ Poly_adjust = 0; /* adjust channel counter */ Div_n_cnt[next_event] += Div_n_max[next_event]; /* From here, a good understanding of the hardware is required */ /* to understand what is happening. I won't be able to provide */ /* much description to explain it here. */ /* if the output is pure or the output is poly5 and the poly5 bit */ /* is set */ if ((AUDC[next_event] & NOTPOLY5) || bit5[P5]) { /* if the PURE bit is set */ if (AUDC[next_event] & PURE) { /* then simply toggle the output */ Outbit[next_event] = !Outbit[next_event]; } /* otherwise if POLY4 is selected */ else if (AUDC[next_event] & POLY4) { /* then use the poly4 bit */ Outbit[next_event] = bit4[P4]; } else { /* otherwise use the poly17 bit */ Outbit[next_event] = bit17[P17]; } } /* At this point I haven't emulated the filters. Though I don't expect it to be complicated, I don't believe this feature is used much anyway. I'll work on it later. */ if ((next_event == CHAN1) || (next_event == CHAN3)) { /* INSERT FILTER HERE */ } /* if the current output bit is set */ if (Outbit[next_event]) { /* then set to the current volume */ Outvol[next_event] = AUDC[next_event] & VOLUME_MASK; } else { /* set the volume to zero */ Outvol[next_event] = 0; } } else /* otherwise we're processing a sample */ { /* adjust the sample counter - note we're using the 24.8 integer which includes an 8 bit fraction for accuracy */ *Samp_n_cnt += Samp_n_max; cur_val = 0; /* add the output values of all 4 channels */ for (chan = CHAN1; chan <= CHAN4; chan++) { cur_val += Outvol[chan]; } /* multiply the volume by 4 and add 8 to center around 128 */ /* NOTE: this statement could be eliminated for efficiency, */ /* though the volume would be lower. */ cur_val = (cur_val << 2) + 8; /* add the current value to the output buffer */ *buffer++ = cur_val; /* and indicate one less byte in the buffer */ n--; } } } /*****************************************************************************/ /* Module: Pokey_process() */ /* Purpose: To fill the output buffer with the sound output based on the */ /* pokey chip parameters. This routine has not been optimized. */ /* Though it is not used by the program, I've left it for reference. */ /* */ /* Author: Ron Fries */ /* Date: September 22, 1996 */ /* */ /* Inputs: *buffer - pointer to the buffer where the audio output will */ /* be placed */ /* n - size of the playback buffer */ /* */ /* Outputs: the buffer will be filled with n bytes of audio - no return val */ /* */ /*****************************************************************************/ void Pokey_process(register unsigned char *buffer, register uint16 n) { register uint32 *div_n_ptr; register uint32 *samp_cnt_w_ptr; register uint32 event_min; register uint8 next_event; register uint8 cur_val; register uint8 *out_ptr; register uint8 audc; register uint8 toggle; /* set a pointer to the whole portion of the samp_n_cnt */ samp_cnt_w_ptr = (uint32 *) ((uint8 *) (&Samp_n_cnt[0]) + 1); /* set a pointer for optimization */ out_ptr = Outvol; /* The current output is pre-determined and then adjusted based on each */ /* output change for increased performance (less over-all math). */ /* add the output values of all 4 channels */ cur_val = 2; /* start with a small offset */ cur_val += *out_ptr++; cur_val += *out_ptr++; cur_val += *out_ptr++; cur_val += *out_ptr++; /* loop until the buffer is filled */ while (n) { /* Normally the routine would simply decrement the 'div by N' */ /* counters and react when they reach zero. Since we normally */ /* won't be processing except once every 80 or so counts, */ /* I've optimized by finding the smallest count and then */ /* 'accelerated' time by adjusting all pointers by that amount. */ /* find next smallest event (either sample or chan 1-4) */ next_event = SAMPLE; event_min = *samp_cnt_w_ptr; /* Though I could have used a loop here, this is faster */ div_n_ptr = Div_n_cnt; if (*div_n_ptr <= event_min) { event_min = *div_n_ptr; next_event = CHAN1; } div_n_ptr++; if (*div_n_ptr <= event_min) { event_min = *div_n_ptr; next_event = CHAN2; } div_n_ptr++; if (*div_n_ptr <= event_min) { event_min = *div_n_ptr; next_event = CHAN3; } div_n_ptr++; if (*div_n_ptr <= event_min) { event_min = *div_n_ptr; next_event = CHAN4; } /* decrement all counters by the smallest count found */ /* again, no loop for efficiency */ *div_n_ptr -= event_min; div_n_ptr--; *div_n_ptr -= event_min; div_n_ptr--; *div_n_ptr -= event_min; div_n_ptr--; *div_n_ptr -= event_min; *samp_cnt_w_ptr -= event_min; /* since the polynomials require a mod (%) function which is division, I don't adjust the polynomials on the SAMPLE events, only the CHAN events. I have to keep track of the change, though. */ Poly_adjust += event_min; /* if the next event is a channel change */ if (next_event != SAMPLE) { /* shift the polynomial counters */ P4 = (P4 + Poly_adjust) % POLY4_SIZE; P5 = (P5 + Poly_adjust) % POLY5_SIZE; P17 = (P17 + Poly_adjust) % Poly17_size; /* reset the polynomial adjust counter to zero */ Poly_adjust = 0; /* adjust channel counter */ Div_n_cnt[next_event] += Div_n_max[next_event]; /* get the current AUDC into a register (for optimization) */ audc = AUDC[next_event]; /* set a pointer to the current output (for opt...) */ out_ptr = &Outvol[next_event]; /* assume no changes to the output */ toggle = FALSE; /* From here, a good understanding of the hardware is required */ /* to understand what is happening. I won't be able to provide */ /* much description to explain it here. */ /* if the output is pure or the output is poly5 and the poly5 bit */ /* is set */ if ((audc & NOTPOLY5) || bit5[P5]) { /* if the PURE bit is set */ if (audc & PURE) { /* then simply toggle the output */ toggle = TRUE; } /* otherwise if POLY4 is selected */ else if (audc & POLY4) { /* then compare to the poly4 bit */ toggle = (bit4[P4] == !(*out_ptr)); } else { /* otherwise compare to the poly17 bit */ toggle = (bit17[P17] == !(*out_ptr)); } } /* At this point I haven't emulated the filters. Though I don't expect it to be complicated, I don't believe this feature is used much anyway. I'll work on it later. */ if ((next_event == CHAN1) || (next_event == CHAN3)) { /* INSERT FILTER HERE */ } /* if the current output bit has changed */ if (toggle) { if (*out_ptr) { /* remove this channel from the signal */ cur_val -= *out_ptr; /* and turn the output off */ *out_ptr = 0; } else { /* turn the output on */ *out_ptr = audc & VOLUME_MASK; /* and add it to the output signal */ cur_val += *out_ptr; } } } else /* otherwise we're processing a sample */ { /* adjust the sample counter - note we're using the 24.8 integer which includes an 8 bit fraction for accuracy */ *Samp_n_cnt += Samp_n_max; /* add the current value to the output buffer */ *buffer++ = cur_val << 2; /* and indicate one less byte in the buffer */ n--; } } }