Buffer arrangement of a PCM exchange system
First Claim
1. A buffer arrangement of a pulse code multiplex exchange system for compensating both short and long term phase drift of information between a transmitting and a receiving data path, each data path being plesiochronously controlled by a first clock and a second clock, respectively, for transmitting of information blocks each composed of at least one pulse frame being, in turn, divided into a plurality of code words each representing a sample of a corresponding channel, said buffer arrangement comprising in combination:
- (a) an alignment buffer connected between the first and the second data path and being composed of two sections, each having a capacity for storing alternately one of two subsequent information blocks in continuous storage locations;
(b) buffer addressing means associated with said alignment buffer for selecting write addresses and read addresses;
(c) address generating means connected to said buffer addressing means for generating consecutive write addresses for said alignment buffer under control of said first clock and for generating consecutive read addresses under control of said second clock;
(d) means for monitoring an offset between a current read address and the respective write address with respect to a predetermined minimal guard distance and for initiating a slip operation whenever said offset falls short of the guard distance, wherein said slip operation constitutes a read address jump from a storage location of one alignment buffer section to the corresponding storage location of the other alignment buffer section and this address jump is achieved by complementing the read address bit identifying a respective one of the alignment buffer sections; and
(e) means for solving access conflicts to said alignment buffer in case of simultaneous requests for read and write operations by granting the type of information requested first without completely suppressing a subsequent request for the other type of operation.
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Accused Products
Abstract
A pulse code multiplex exchange system includes a buffer arrangement for compensating both short and long term phase drift of information between plesiochronous data paths each being controlled for block information transfer by a separate clock. An alignment buffer is arranged between the two data paths. It has two sections, each having a capacity for storing alternately one of two subsequent information blocks, and on chip address decoders for selecting write and read addresses. Separate address generators are associated with the buffer for generating consecutive write addresses under control of a first clock and read addresses under control of a second clock, respectively. A guard distance detector continuously monitors the distance between the present write address and the respective read address, and initiates a slip operation for switching subsequent read operations from one section of the alignment buffer to the other section, if the address distance falls short of a minimal guard distance.
33 Citations
4 Claims
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1. A buffer arrangement of a pulse code multiplex exchange system for compensating both short and long term phase drift of information between a transmitting and a receiving data path, each data path being plesiochronously controlled by a first clock and a second clock, respectively, for transmitting of information blocks each composed of at least one pulse frame being, in turn, divided into a plurality of code words each representing a sample of a corresponding channel, said buffer arrangement comprising in combination:
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(a) an alignment buffer connected between the first and the second data path and being composed of two sections, each having a capacity for storing alternately one of two subsequent information blocks in continuous storage locations; (b) buffer addressing means associated with said alignment buffer for selecting write addresses and read addresses; (c) address generating means connected to said buffer addressing means for generating consecutive write addresses for said alignment buffer under control of said first clock and for generating consecutive read addresses under control of said second clock; (d) means for monitoring an offset between a current read address and the respective write address with respect to a predetermined minimal guard distance and for initiating a slip operation whenever said offset falls short of the guard distance, wherein said slip operation constitutes a read address jump from a storage location of one alignment buffer section to the corresponding storage location of the other alignment buffer section and this address jump is achieved by complementing the read address bit identifying a respective one of the alignment buffer sections; and (e) means for solving access conflicts to said alignment buffer in case of simultaneous requests for read and write operations by granting the type of information requested first without completely suppressing a subsequent request for the other type of operation. - View Dependent Claims (2, 3, 4)
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Specification