myfm.cpp

   1 // DGen v1.06+
   2 // MYFM.CPP - interface to YM2612Update
   3
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include "md.h"
   7
   8 extern int sound_is_okay;
   9
  10 // md.h also has include fm.h
  11
  12 // REMEMBER NOT TO USE ANY STATIC variables, because they
  13 // will exist thoughout ALL megadrives!
  14
  15 int md::flush_fm_to_mame()
  16 {
  17   int sid,r;
  18   // If we reset mame's ym2612 code, we need to pass all the values
  19   // to it again
  20   for (sid=0;sid<2;sid++)
  21   {
  22     for (r=0;r<0x100;r++)
  23     {
  24       if (sound_is_okay)
  25       {
  26         if (fm_reg[sid][r]!=-1)
  27         {
  28           YM2612Write(0,sid*2+0,r); // select reg r
  29           YM2612Write(0,sid*2+1,fm_reg[sid][r]); // Write data
  30         }
  31       }
  32     }
  33   }
  34
  35   return 0;
  36 }
  37
  38 int md::myfm_write(int a,int v,int md)
  39 {
  40   int sid=0;
  41   int mame_can_have_it=1;
  42
  43   (void)md;
  44
  45   a&=3;
  46
  47   sid=(a&2)?1:0;
  48
  49   if ((a&1)==0) fm_sel[sid]=v;
  50   else
  51   {
  52     // stash all values
  53     fm_reg[sid] [fm_sel[sid]&0xff] = v;
  54
  55     if (fm_sel[sid]==0x2a) { dac_submit(v); mame_can_have_it=0; }
  56     if (fm_sel[sid]==0x2b) { dac_enable(v); mame_can_have_it=0; }
  57
  58     if ((fm_sel[sid]&0xfc)==0x24) { mame_can_have_it=0; }
  59
  60     if (fm_sel[sid]==0x27)
  61     {
  62       if (v&0x10) fm_tover[0]&=~1;
  63       if (v&0x20) fm_tover[0]&=~2;
  64       // timer ack?
  65     }
  66
  67   }
  68
  69   if (sound_is_okay && mame_can_have_it)
  70     YM2612Write(0,a&3,v);
  71
  72   return 0;
  73 }
  74
  75 int md::myfm_read(int a)
  76 {
  77   if ((a&1)==0)
  78     return fm_tover[0];
  79   else
  80   {
  81     if (sound_is_okay) YM2612Read(0,a&3);
  82   }
  83   return 0;
  84 }
  85
  86 int md::mysn_write(int d)
  87 {
  88   if (sound_is_okay) SN76496Write(0,d);
  89   return 0;
  90 }
  91
  92 // This called once per raster
  93 int md::fm_timer_callback()
  94 {
  95   int amax,bmax, i;
  96
  97   // Our raster lasts 63.61323 microseconds
  98   for (i=0;i<4;i++) ras_fm_ticker[i]+=64;
  99
 100 //  if (sound_is_okay) ret=YM2612Read(0,a&3);
 101
 102   // period of timer a is
 103   // 18 * (1024 - ((fm_reg[0][0x24]<<2)+(fm_reg[0][0x25])&3))) microsecs
 104
 105   amax=18 * (1024 -  ((fm_reg[0][0x24]<<2)+(fm_reg[0][0x25]&3)) );
 106   bmax=288*(256-fm_reg[0][0x26]);
 107
 108   if (bmax<=0) bmax=1;
 109   if (amax<=0) amax=1;
 110
 111   if (ras_fm_ticker[0]>=amax)
 112   {
 113     fm_tover[0]|=1; ras_fm_ticker[0]-=amax;
 114   }
 115
 116   if (ras_fm_ticker[1]>=bmax)
 117   {
 118     fm_tover[0]|=2; ras_fm_ticker[1]-=bmax;
 119   }
 120   return 0;
 121 }