I2C_DATA_REG
i2c_write_reg(sc, I2C_DATA_REG, slave);
i2c_write_reg(sc, I2C_DATA_REG, slave);
i2c_read_reg(sc, I2C_DATA_REG);
reg = i2c_read_reg(sc, I2C_DATA_REG);
i2c_write_reg(sc, I2C_DATA_REG, *buf++);
i2c_write_reg(sc, I2C_DATA_REG, slave);
i2c_write_reg(sc, I2C_DATA_REG, slave);
i2c_read_reg(sc, I2C_DATA_REG);
*buf++ = i2c_read_reg(sc, I2C_DATA_REG);
i2c_write_reg(sc, I2C_DATA_REG, *buf++);