ZX Spectrum Next DMA Layer 2 Screen Clearing

layer2dmaclear

// R3G3B2
void clearLayer2Screen(unsigned char colour)
{
   unsigned char zero = colour;

   IO_123B = 0x03;   // Top
   // WR0
   IO_6B = 0x79;
   IO_6B = 0x00; IO_6B = 0x00; // A Start
   IO_6B = 0x00; IO_6B = 0x40; // 16k

   // WR1
   IO_6B = 0x14;
   // WR2
   IO_6B = 0x30;
   // WR4
   IO_6B = 0xAD;
   IO_6B = (int)(&zero) & 0x00FF;
   IO_6B = ((int)(&zero) & 0xFF00) >> 8;
   // WR5
   IO_6B = 0x82; 
   // WR6 (load)
   IO_6B = 0xCF;
   // WR6 (enable)
   IO_6B = 0x87;

   IO_123B = 0x43; // Middle
   // WR6 (disable)
   IO_6B = 0x83;
   // WR6 (load)
   IO_6B = 0xCF;
   // WR6 (enable)
   IO_6B = 0x87;
   
   IO_123B = 0x83;   // Bottom
   // WR6 (disable)
   IO_6B = 0x83;
   // WR6 (load)
   IO_6B = 0xCF;
   // WR6 (enable)
   IO_6B = 0x87;
}