Patent ID: 7804861

Claim:
A demultiplexer, comprising: packet identifier filters adapted to extract digital broadcasting streams and output the extracted digital broadcasting streams; a first memory adapted to receive the extracted digital broadcasting streams, store the digital broadcasting streams in a word unit, generate write request signals for words of a corresponding broadcasting channel, and output the words in response to grant signals; an arbiter adapted to determine priorities of a read request signal and corresponding write request signals of the digital broadcasting streams, and generate the grant signals corresponding to the priorities, to arbitrate read and write access to the digital broadcasting streams; a conditional access buffer adapted to store the digital broadcasting streams output from the first memory in response to the grant signals, and output the corresponding digital broadcasting streams in response to the grant signals; a conditional access module adapted to receive the digital broadcasting streams output from the conditional access buffer, descramble the received digital broadcasting streams, and generate a buffer read request signal when the received digital broadcasting streams are descrambled; and an external memory adapted to allow the digital broadcasting streams stored in the word unit in the first memory to be bypassed and to be temporarily stored under a direct memory access control when usage of the conditional access buffer is greater than a threshold level; wherein the conditional access buffer has a single port memory format, and wherein the write request signal corresponding to the broadcasting channel in which the bypassed words have been output is excluded from the determination of priority.