By assigning a slave unit and at least one master unit in a buffer controller, clocks of the at least one master unit can be unified with a clock of the slave unit. A buffer status array is assigned for the slave unit in a buffer, and either a range status array or a queue status array is assigned for the master unit in the buffer for performing operations of the buffer controller in an accessing-by-block manner or in an accessing-by-spaced-interval manner. The master unit cooperated with the slave unit is determined from the at least one master unit by using a starvation-preventing algorithm.