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ay8910.c:
* Fixes mantis bugs 01767, 01769 * Corrected some comments
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Couriersud
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@ -39,8 +39,8 @@
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This is backed by oscilloscope pictures from the datasheet. If a fixed volume
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is set, i.e. enveloppe is disabled, the output voltage is set to 0V. Recordings
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I found on the web for gyruss indicate, that the AY-3-8910 offset should
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be around 1.5V. This will also make sound levels more compatible with
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user descriptions.
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be around 0.2V. This will also make sound levels more compatible with
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user observations for scramble.
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The Model:
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5V 5V
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@ -66,33 +66,34 @@ where used to calibrate channel mixing for the YM2149. This was done using
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a least square approach using a fixed RL of 1K Ohm.
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For the AY measurements cited in e.g. openmsx as "Hacker Kay" for a single
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channel were taken. These were normalized to 0 ... 65535 and adapted to on
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offset of 1.5V and a VPP of 1.3V.
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channel were taken. These were normalized to 0 ... 65535 and consequently
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adapted to an offset of 0.2V and a VPP of 1.3V. These measurements are in
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line e.g. with the formula used by pcmenc for the volume: vol(i) = exp(i/2-7.5).
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The following is documentation from the code moved here and amended to reflect
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the changes done:
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Careful studies of the chip output prove that the chip counts up from 0
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until the counter becomes greater or equal to the period. This is an
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important difference when the program is rapidly changing the period to
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modulate the sound. This is worthwhile noting, since the datasheets
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until the counter becomes greater or equal to the period. This is an
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important difference when the program is rapidly changing the period to
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modulate the sound. This is worthwhile noting, since the datasheets
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say, that the chip counts down.
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Also, note that period = 0 is the same as period = 1. This is mentioned
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in the YM2203 data sheets. However, this does NOT apply to the Envelope
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period. In that case, period = 0 is half as period = 1.
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Envelope shapes:
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C AtAlH
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0 0 x x \___
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0 1 x x /___
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1 0 0 0 \\\\
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1 0 0 1 \___
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1 0 1 0 \/\/
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1 0 1 1 \```
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1 1 0 0 ////
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1 1 0 1 /```
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1 1 1 0 /\/\
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1 1 1 1 /___
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C AtAlH
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0 0 x x \___
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0 1 x x /___
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1 0 0 0 \\\\
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1 0 0 1 \___
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1 0 1 0 \/\/
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1 0 1 1 \```
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1 1 0 0 ////
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1 1 0 1 /```
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1 1 1 0 /\/\
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1 1 1 1 /___
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The envelope counter on the AY-3-8910 has 16 steps. On the YM2149 it
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has twice the steps, happening twice as fast.
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@ -190,7 +191,7 @@ struct _ay8910_context
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/*************************************
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*
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* Static
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* Static
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*
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*************************************/
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@ -262,7 +263,7 @@ static const ay_ym_param ay8910_param =
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/*************************************
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*
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* Inline
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* Inline
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*
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*************************************/
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@ -310,7 +311,7 @@ INLINE void build_3D_table(double rl, const ay_ym_param *par, const ay_ym_param
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if (normalize)
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{
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for (j=0; j < 32*32*32*8; j++)
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tab[j] = MAX_OUTPUT * (((temp[j] - min)/(max-min)) - 0.25) * factor;
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tab[j] = MAX_OUTPUT * (((temp[j] - min)/(max-min))) * factor;
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}
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else
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{
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@ -379,7 +380,7 @@ INLINE UINT16 mix_3D(ay8910_context *psg)
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/*************************************
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*
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* Static functions
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* Static functions
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*
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*************************************/
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@ -546,7 +547,7 @@ static void ay8910_update(void *param,stream_sample_t **inputs, stream_sample_t
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if (psg->holding == 0)
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{
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psg->count_env++;
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if (psg->count_env >= ENVELOPE_PERIOD(psg) * psg->step )
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if (psg->count_env >= ENVELOPE_PERIOD(psg) * psg->step )
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{
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psg->count_env = 0;
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psg->env_step--;
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@ -619,9 +620,9 @@ static void build_mixer_table(ay8910_context *psg)
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build_single_table(psg->intf->res_load[chan], psg->par_env, normalize, psg->env_table[chan], 0);
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}
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/*
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* The previous implementation added all three channels up instead of averaging them.
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* The factor of 3 will force the same levels if normalizing is used.
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*/
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* The previous implementation added all three channels up instead of averaging them.
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* The factor of 3 will force the same levels if normalizing is used.
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*/
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build_3D_table(psg->intf->res_load[0], psg->par, psg->par_env, normalize, 3, psg->zero_is_off, psg->vol3d_table);
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}
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@ -650,8 +651,8 @@ static void ay8910_statesave(ay8910_context *psg, int sndindex)
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/*************************************
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*
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* Public functions
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*
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* Public functions
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*
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* used by e.g. YM2203, YM2210 ...
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*
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*************************************/
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@ -812,7 +813,7 @@ int ay8910_read_ym(void *chip)
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/*************************************
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*
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* Sound Interface
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*
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*
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*************************************/
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static void *ay8910_start(int sndindex, int clock, const void *config)
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@ -947,7 +948,7 @@ void ymz294_get_info(void *token, UINT32 state, sndinfo *info)
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/*************************************
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*
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* Read/Write Handlers
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*
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*
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*************************************/
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READ8_HANDLER( AY8910_read_port_0_r ) { return ay8910_read_ym(sndti_token(SOUND_AY8910, 0)); }
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