REX3_XYSTARTI_XSHIFT
rex3_write(dc, REX3_REG_XYSTARTI, (x << REX3_XYSTARTI_XSHIFT) | y);
rex3_write(dc, REX3_REG_XYSTARTI, (x1 << REX3_XYSTARTI_XSHIFT) | y1);
rex3_write(dc, REX3_REG_XYSTARTI, (xs << REX3_XYSTARTI_XSHIFT) | ys);