license info added to Pico directory

[cyclone68000.git] / Pico / VideoPort.cpp

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// This file is part of the PicoDrive Megadrive Emulator\r
\r
// This code is licensed under the GNU General Public License version 2.0 and the MAME License.\r
// You can choose the license that has the most advantages for you.\r
\r
// SVN repository can be found at http://code.google.com/p/cyclone68000/\r
\r
#include "PicoInt.h"\r
\r
static inline void AutoIncrement()\r
{\r
  Pico.video.addr=(unsigned short)(Pico.video.addr+Pico.video.reg[0xf]);\r
}\r
\r
static void VideoWrite(unsigned int d)\r
{\r
  unsigned int a=0;\r
  unsigned short sd=(unsigned short)d;\r
\r
  a=Pico.video.addr;\r
  if (a&1) d=((d<<8)&0xff00)|(d>>8); // If address is odd, bytes are swapped\r
  a>>=1;\r
\r
  switch (Pico.video.type)\r
  {\r
    case 1: Pico.vram [a&0x7fff]=sd; break;\r
    case 3: Pico.cram [a&0x003f]=sd; Pico.m.dirtyPal=1; break;\r
    case 5: Pico.vsram[a&0x003f]=sd; break;\r
  }\r
  \r
  AutoIncrement();\r
}\r
\r
static unsigned int VideoRead()\r
{\r
  unsigned int a=0,d=0;\r
\r
  a=Pico.video.addr; a>>=1;\r
\r
  switch (Pico.video.type)\r
  {\r
    case 0: d=Pico.vram [a&0x7fff]; break;\r
    case 8: d=Pico.cram [a&0x003f]; break;\r
    case 4: d=Pico.vsram[a&0x003f]; break;\r
  }\r
  \r
  AutoIncrement();\r
  return d;\r
}\r
\r
static int GetDmaSource()\r
{\r
  struct PicoVideo *pvid=&Pico.video;\r
  int source=0;\r
  source =pvid->reg[0x15]<<1;\r
  source|=pvid->reg[0x16]<<9;\r
  source|=pvid->reg[0x17]<<17;\r
  return source;\r
}\r
\r
static int GetDmaLength()\r
{\r
  struct PicoVideo *pvid=&Pico.video;\r
  int len=0;\r
  // 16-bit words to transfer:\r
  len =pvid->reg[0x13];\r
  len|=pvid->reg[0x14]<<8;\r
  return len;\r
}\r
\r
static void DmaSlow(int source,int len)\r
{\r
  int i=0,max=0;\r
\r
  if (source>=0x800000 && source<0xe00000) return; // Invalid source address\r
\r
  /// Clip Cram DMA size (Todds Adventures in Slime World):\r
  if (Pico.video.type==3) { max=0x80-Pico.video.addr; if (len>max) len=max; }\r
\r
  for (i=0;i<len;i++)\r
  {\r
    VideoWrite(PicoRead16(source));\r
    source+=2;\r
  }\r
}\r
\r
static void DmaCopy(int source,int len)\r
{\r
  int i=0;\r
\r
  len>>=1; // Length specifies number of bytes\r
\r
  for (i=0;i<len;i++)\r
  {\r
    VideoWrite(Pico.vram[source&0x7fff]);\r
    source+=2;\r
  }\r
}\r
\r
static void DmaFill(int data)\r
{\r
  int len=0,i=0;\r
  \r
  len=GetDmaLength();\r
\r
  for (i=0;i<len+1;i++) VideoWrite(data);\r
}\r
\r
static void CommandDma()\r
{\r
  struct PicoVideo *pvid=&Pico.video;\r
  int len=0,method=0,source=0;\r
\r
  if ((pvid->reg[1]&0x10)==0) return; // DMA not enabled\r
\r
  len=GetDmaLength();\r
\r
  method=pvid->reg[0x17]>>6;\r
  source=GetDmaSource();\r
  if (method< 2) DmaSlow(source,len); // 68000 to VDP\r
  if (method==3) DmaCopy(source,len); // VRAM Copy\r
}\r
\r
static void CommandChange()\r
{\r
  struct PicoVideo *pvid=&Pico.video;\r
  unsigned int cmd=0,addr=0;\r
\r
  cmd=pvid->command;\r
\r
  // Get type of transfer 0xc0000030 (v/c/vsram read/write)\r
  pvid->type=(unsigned char)(((cmd>>2)&0xc)|(cmd>>30));\r
\r
  // Get address 0x3fff0003\r
  addr =(cmd>>16)&0x3fff;\r
  addr|=(cmd<<14)&0xc000;\r
  pvid->addr=(unsigned short)addr;\r
\r
  // Check for dma:\r
  if (cmd&0x80) CommandDma();\r
}\r
\r
void PicoVideoWrite(unsigned int a,unsigned int d)\r
{\r
  struct PicoVideo *pvid=&Pico.video;\r
\r
  a&=0x1c;\r
  d=(unsigned short)d;\r
\r
  if (a==0x00) // Data port 0 or 2\r
  {    \r
    if (pvid->pending) CommandChange();\r
    pvid->pending=0;\r
\r
    // If a DMA fill has been set up, do it\r
    if ((pvid->command&0x80) && (pvid->reg[1]&0x10) && (pvid->reg[0x17]>>6)==2)\r
    {\r
      DmaFill(d);\r
    }\r
    else\r
    {\r
      VideoWrite(d);\r
    }\r
    return;\r
  }\r
\r
  if (a==0x04) // Command port 4 or 6\r
  {\r
    if (pvid->pending)\r
    {\r
      // Low word of command:\r
      pvid->command&=0xffff0000;\r
      pvid->command|=d;\r
      pvid->pending=0;\r
      CommandChange();\r
      return;\r
    }\r
\r
    if ((d&0xc000)==0x8000)\r
    {\r
      // Register write:\r
      int num=(d>>8)&0x1f;\r
      pvid->reg[num]=(unsigned char)d;\r
      return;\r
    }\r
\r
    // High word of command:\r
    pvid->command&=0x0000ffff;\r
    pvid->command|=d<<16;\r
    pvid->pending=1;\r
  }\r
}\r
\r
unsigned int PicoVideoRead(unsigned int a)\r
{\r
  unsigned int d=0;\r
  \r
  a&=0x1c;\r
\r
  if (a==0x00) { d=VideoRead(); goto end; }\r
\r
  if (a==0x04)\r
  {\r
    d=Pico.video.status;\r
\r
    // Toggle fifo full empty:\r
    if (Pico.m.rotate&4) d|=0x3520; else d|=0x3620;\r
    if (Pico.m.rotate&2) d|=0x0004; // Toggle in/out of H-Blank\r
    Pico.m.rotate++;\r
\r
    if (Pico.m.pal) d|=1; // PAL screen\r
\r
    goto end;\r
  }\r
\r
  if ((a&0x1c)==0x08)\r
  {\r
    if (Pico.m.scanline>-64) d=Pico.m.scanline; // HV-Counter\r
    else                     d=Pico.m.rotate++; // Fudge\r
\r
    d&=0xff; d<<=8;\r
    goto end;\r
  }\r
\r
end:\r
\r
  return d;\r
}\r