void *copperlist = AllocMem(1000, MEMF_CHIP|MEMF_CLEAR);
UWORD *copperlist_ptr = (UWORD *)copperlist;

// add a bitplane
*(copperlist_ptr)++ = BPL1PTH;
*(copperlist_ptr)++ = ((ULONG)bitplane >> 16) & 0xffff;
*(copperlist_ptr)++ = BPL1PTL;
*(copperlist_ptr)++ = (ULONG)bitplane & 0xffff;

// add a color
*(copperlist_ptr)++ = COLOR00;
*(copperlist_ptr)++ = 0x000;

// add a WAIT
*(copperlist_ptr)++ = ((currentY & 0xff) << 8) | 0x26 | 0x1;
*(copperlist_ptr)++ = 0xfffe;

// do a PAL workaround
if (currentY == 255) {
  *(copperlist_ptr++) = 0xffdf;
  *(copperlist_ptr++) = 0xfffe;
}

// add an END
*(copperlist_ptr)++ = 0xffff;
*(copperlist_ptr)++ = 0xfffe;