BUFFERING DEVICE AND CONTROL METHOD THEREOF

By a buffering device, a first holding unit holds a write number value and a read number value for each of a plurality of grouping criteria. The grouping criteria include a priority of data units as one grouping parameter. A second holding unit holds a plurality of transmission commands. The plurality of transmission commands correspond to any of the plurality of grouping criteria. A control unit forms a "holding address" for causing the second holding unit to hold the written transmission commands in the second holding unit based on the write number value for the grouping criteria corresponding to the written transmission commands. The control unit forms an "output address" of the second holding unit, in which the read transmission commands are held, based on the information on the read number value for the grouping criteria corresponding to the read transmission commands.