dac_write
dac_write(par, BT459_ADDR_LO, regno);
dac_write(par, BT459_ADDR_HI, 0x00);
dac_write(par, BT459_CMAP, red);
dac_write(par, BT459_CMAP, green);
dac_write(par, BT459_CMAP, blue);
dac_write(par, BT459_ADDR_LO, 0x00);
dac_write(par, BT459_ADDR_HI, 0x03);
dac_write(par, BT459_DATA, 0x00);
dac_write(par, BT459_ADDR_LO, regno);
dac_write(par, BT459_ADDR_HI, 0x00);
dac_write(par, BT459_CMAP, red);
dac_write(par, BT459_CMAP, green);
dac_write(par, BT459_CMAP, blue);
dac_write(par, BT459_ADDR_LO, 0x00);
dac_write(par, BT459_ADDR_HI, 0x03);
dac_write(par, BT459_DATA, 0x00);