// license:BSD-3-Clause // copyright-holders:Derrick Renaud /************************************************************************* audio\nitedrvr.c *************************************************************************/ #include "emu.h" #include "includes/nitedrvr.h" #include "sound/discrete.h" /* Discrete Sound Emulation */ static const discrete_lfsr_desc nitedrvr_lfsr = { DISC_CLK_IS_FREQ, 16, /* Bit Length */ 0, /* Reset Value */ 0, /* Use Bit 0 as XOR input 0 */ 14, /* Use Bit 14 as XOR input 1 */ DISC_LFSR_XNOR, /* Feedback stage1 is XNOR */ DISC_LFSR_OR, /* Feedback stage2 is just stage 1 output OR with external feed */ DISC_LFSR_REPLACE, /* Feedback stage3 replaces the shifted register contents */ 0x000001, /* Everything is shifted into the first bit only */ 0, /* Output is already inverted by XNOR */ 15 /* Output bit */ }; /* Nodes - Sounds */ #define NITEDRVR_NOISE NODE_10 #define NITEDRVR_BANG_SND NODE_11 #define NITEDRVR_MOTOR_SND NODE_12 #define NITEDRVR_SCREECH1_SND NODE_13 #define NITEDRVR_SCREECH2_SND NODE_14 DISCRETE_SOUND_START(nitedrvr_discrete) /************************************************/ /* nitedrvr Effects Relataive Gain Table */ /* */ /* Effect V-ampIn Gain ratio Relative */ /* Bang 3.8 5/(5+6.8) 1000.0 */ /* Motor 3.8 5/(5+10) 786.7 */ /* Screech1 3.8 5/(5+47) 226.9 */ /* Screech2 3.8 5/(5+47) 226.9 */ /************************************************/ /************************************************/ /* Input register mapping for nitedrvr */ /************************************************/ /* NODE GAIN OFFSET INIT */ DISCRETE_INPUTX_DATA (NITEDRVR_BANG_DATA, 1000.0/15, 0.0, 0.0) DISCRETE_INPUT_LOGIC (NITEDRVR_SKID1_EN) DISCRETE_INPUT_LOGIC (NITEDRVR_SKID2_EN) DISCRETE_INPUTX_DATA (NITEDRVR_MOTOR_DATA, -1, 0x0f, 0) DISCRETE_INPUT_LOGIC (NITEDRVR_CRASH_EN) DISCRETE_INPUT_NOT (NITEDRVR_ATTRACT_EN) /************************************************/ /* NOTE: Motor circuit is a rip from Sprint for */ /* now. This will have to be converted to 566. */ /* */ /* Motor sound circuit is based on a 556 VCO */ /* with the input frequency set by the MotorSND */ /* latch (4 bit). This freqency is then used to */ /* driver a modulo 12 counter, with div6, 4 & 3 */ /* summed as the output of the circuit. */ /* VCO Output is Sq wave = 27-382Hz */ /* F1 freq - (Div6) */ /* F2 freq = (Div4) */ /* F3 freq = (Div3) 33.3% duty, 33.3 deg phase */ /* To generate the frequency we take the freq. */ /* diff. and /15 to get all the steps between */ /* 0 - 15. Then add the low frequency and send */ /* that value to a squarewave generator. */ /* Also as the frequency changes, it ramps due */ /* to a 2.2uf capacitor on the R-ladder. */ /* Note the VCO freq. is controlled by a 250k */ /* pot. The freq. used here is for the pot set */ /* to 125k. The low freq is allways the same. */ /* This adjusts the high end. */ /* 0k = 214Hz. 250k = 4416Hz */ /************************************************/ DISCRETE_RCFILTER(NODE_20, NITEDRVR_MOTOR_DATA, 123037, 2.2e-6) DISCRETE_ADJUSTMENT(NODE_21, (214.0-27.0)/12/31, (4416.0-27.0)/12/31, DISC_LOGADJ, "MOTOR") DISCRETE_MULTIPLY(NODE_22, NODE_20, NODE_21) DISCRETE_MULTADD(NODE_23, NODE_22, 2, 27.0/6) /* F1 = /12*2 = /6 */ DISCRETE_SQUAREWAVE(NODE_24, 1, NODE_23, (786.7/3), 50.0, 0, 0) DISCRETE_RCFILTER(NODE_25, NODE_24, 10000, 1e-7) DISCRETE_MULTADD(NODE_26, NODE_22, 3, 27.0/4) /* F2 = /12*3 = /4 */ DISCRETE_SQUAREWAVE(NODE_27, 1, NODE_26, (786.7/3), 50.0, 0, 0) DISCRETE_RCFILTER(NODE_28, NODE_27, 10000, 1e-7) DISCRETE_MULTADD(NODE_29, NODE_22, 4, 27.0/3) /* F3 = /12*4 = /3 */ DISCRETE_SQUAREWAVE(NODE_30, 1, NODE_29, (786.7/3), 100.0/3, 0, 360.0/3) DISCRETE_RCFILTER(NODE_31, NODE_30, 10000, 1e-7) DISCRETE_ADDER3(NITEDRVR_MOTOR_SND, NITEDRVR_ATTRACT_EN, NODE_25, NODE_28, NODE_31) /************************************************/ /* Bang circuit is built around a noise */ /* generator built from 2 shift registers that */ /* are clocked by the 4V signal. */ /* 4V = HSYNC/2/4 */ /* = 15750/2/4 */ /* Output is integrated to apply decay. */ /************************************************/ DISCRETE_LFSR_NOISE(NITEDRVR_NOISE, NITEDRVR_CRASH_EN, NITEDRVR_CRASH_EN, 15750.0/2/4, 1.0, 0, 0, &nitedrvr_lfsr) DISCRETE_MULTIPLY(NODE_62, NITEDRVR_NOISE, NITEDRVR_BANG_DATA) DISCRETE_RCFILTER(NITEDRVR_BANG_SND, NODE_62, 545.6, 3.3e-7) /************************************************/ /* Skid circuits ripped from other drivers */ /* for now. */ /* */ /* Skid circuits takes the noise output from */ /* the crash circuit and applies +ve feedback */ /* to cause oscillation. There is also an RC */ /* filter on the input to the feedback cct. */ /* RC is 1K & 10uF */ /* Feedback cct is modelled by using the RC out */ /* as the frequency input on a VCO, */ /* breadboarded freq range as: */ /* 0 = 940Hz, 34% duty */ /* 1 = 630Hz, 29% duty */ /* the duty variance is so small we ignore it */ /************************************************/ DISCRETE_INVERT(NODE_70, NITEDRVR_NOISE) DISCRETE_RCFILTER(NODE_71, NODE_70, 1000, 1e-5) DISCRETE_MULTADD(NODE_72, NODE_71, 940.0-630.0, ((940.0-630.0)/2)+630.0) DISCRETE_SQUAREWAVE(NITEDRVR_SCREECH1_SND, NITEDRVR_SKID1_EN, NODE_72, 226.9, 31.5, 0, 0.0) DISCRETE_MULTADD(NODE_75, NODE_71, 1380.0-626.0, 626.0+((1380.0-626.0)/2)) /* Frequency */ DISCRETE_MULTADD(NODE_76, NODE_71, 32.0-13.0, 13.0+((32.0-13.0)/2)) /* Duty */ DISCRETE_SQUAREWAVE(NITEDRVR_SCREECH2_SND, NITEDRVR_SKID2_EN, NODE_75, 226.9, NODE_76, 0, 0.0) /************************************************/ /* Combine all sound sources. */ /* Add some final gain to get to a good sound */ /* level. */ /************************************************/ DISCRETE_ADDER4(NODE_90, 1, NITEDRVR_MOTOR_SND, NITEDRVR_BANG_SND, NITEDRVR_SCREECH1_SND, NITEDRVR_SCREECH2_SND) DISCRETE_OUTPUT(NODE_90, 65534.0/(786.7+1000.0+226.9)) DISCRETE_SOUND_END