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Buffer queue write pointer control circuit notably for self-channelling packet time-division switching system

  • US 4,933,932 A
  • Filed: 12/21/1988
  • Issued: 06/12/1990
  • Est. Priority Date: 12/24/1987
  • Status: Expired due to Fees
First Claim
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1. A circuit for controlling write pointers of J buffer cell queues temporarily memorizing incoming data groups in chronological order of arrival, where J is a predetermined integer, each of said incoming data groups including a respective channelling word for enabling selection of a respective one of plural buffer queues in one of the cells of which said incoming data group is to be written, a time base providing a cycle of J queue read addresses and a queue cell read pointer to said circuit, said time base incrementing said read pointer by unity during every queue read cycle so as to successively read cells in each of said queues,said circuit comprisingmeans for memorizing decremented values of J write pointers respectively associated with said J buffer queues, a write pointer identifying a cell which is free in the respective queue whereby a further incoming data group including the respective channelling word is written in said free cell of said respective queue,means for reading the memorized decremented value of the write pointer associated with a queue which is selected as a function of said channelling word during writing of an incoming data group in said selected queue and which is selected as a function of said queue read address during reading of an outgoing data group from said selected queue,first means for incrementing by unity the read decremented value of the said write pointer of said selected queue during said outgoing data group reading, thereby deriving a value of said write pointer of said selected queue,second means for incrementing by two units the read decremented value of the write pointer of said selected queue during said incoming data group writing, thereby deriving a value incremented by unity of said write pointer of said selected queue,means for comparing write and read pointers to thereby detect (a) an equality between said value of said write pointer associated with said selected queue and said read pointer value, and (b) an inequality between said incremented-by-one-unit write pointer value and said read point value;

  • andmeans for writing said write pointer value of said selected queue in said memorizing means responsive to one of said equality and inequality detected by said comparing means, said equality being consecutive to said outgoing data group reading from said selected queue, and said inequality being consecutive to said incoming data group writing to said selected queue.

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