define char spi_at250x0_state
define int  spi_at250x0_address
define char spi_at250x0_status
define char spi_at250x0_page
 
func char spi_at250x0 (char st) {
  unsigned char opcode;

  printf ("AT250X0: STATE %u\n", (unsigned) st);

  switch (st)  {
    case 0:  /* Get OPCode */
      opcode = SPI0_OUT & 0x0007;
      printf ("AT250X0: OPCODE %u\n", (unsigned) opcode);

    switch (opcode)
      {
      case 1: /* WRSR */
        return (0);

      case 2: /* Write */
        printf ("AT250X0: WRITE OPCODE Detected\n");
        spi_at250x0_address = (SPI0_OUT & 0x08) << 5;
        return (3);

      case 3: /* Read */
        printf ("AT250X0: READ OPCODE Detected\n");
        spi_at250x0_address = (SPI0_OUT & 0x08) << 5;
        return (1);

      case 4: /* WRDI */
        spi_at250x0_status &= ~0x02; /* Clear Write Enable Bit */
        return (0);

      case 5: /* RDSR */
        SPI0_IN = spi_at250x0_status;
        return (5);

      case 6: /* WREN */
        spi_at250x0_status |= 0x02; /* Set Write Enable Bit */
        return (0);
      }
    return (0);

  case 1:  /* Get Address LSB for READ */
    spi_at250x0_address |= (SPI0_OUT & 0xFF);
    printf ("AT250X0: Address %4.4X Detected\n", spi_at250x0_address);
    return (2);

  case 2:  /* Read */
    printf ("AT250X0: Read %2.2X from address %4.4X\n", _rbyte(0x700000 + spi_at250x0_address), spi_at250x0_address);
    SPI0_IN = _RBYTE(0x700000 + spi_at250x0_address);
    spi_at250x0_address = (spi_at250x0_address + 1) % 512;
    return (2);

  case 3:  /* Get Address LSB for WRITE */
    spi_at250x0_address |= (SPI0_OUT & 0xFF);
	spi_at250x0_page = 0;
    printf ("AT250X0: Address %4.4X Detected\n", spi_at250x0_address);
    return (4);

  case 4:  /* Write */
    if (spi_at250x0_status & 0x02)
      {
      printf ("AT250X0: Write %2.2X to address %4.4X\n", SPI0_OUT, spi_at250x0_address);
      _wbyte(0x700000 + spi_at250x0_address, SPI0_OUT);
	  spi_at250x0_address = (++spi_at250x0_page)&0x07;
      spi_at250x0_status |= 0x01;
      }
    return (4);

  case 5:  /* Instruction End */
    return (5);
  }

return (0);
}

/*
 * This signal function watches the AT89S8252 SPI port for writes.  If there 
 * is an SPI port output and if P1.0 is LO (AT250X0 chip select) then interpret
 * the SPI output data and run the state machine.
 */
signal void spi_watcher (void) 
{

printf("SPI simulation started");
spi_at250x0_state = 0;

while (1) {
  wwatch (SPI0_OUT);
  printf ("SPI0_OUT Detected\n");

  if ((PORT0 & 0x00000400) == 0)				  //chipselect
    {
    printf ("Calling AT250X0 Routines\n");
    spi_at250x0_state = spi_at250x0 (spi_at250x0_state);

    if (spi_at250x0_status & 0x01)
      swatch (0.000100);
      spi_at250x0_status &= ~0x01;
    }
  else
    {
    printf ("Resetting AT250X0 Routines\n");
    spi_at250x0_state = 0;
    }
  }
}

/*-----------------------------------------------
Enable the signal function for SPI writes.
-----------------------------------------------*/
map 0x700000,0x70FFFF READ WRITE
spi_watcher();