Abstract: An apparatus and method for determining an alignment of a codeword is disclosed. A data stream may be received, and a cumulative syndrome value determined. The cumulative syndrome value may be based on error correction and data scrambling operations performed on the data stream. If the cumulative syndrome value matches a predetermined cumulative syndrome value, then alignment of the codeword with respect to the data stream is determined.

Abstract: A method for accumulation of information is described. The information is separated into first portions of MSBs and second portions of LSBs. The first and second portions are respectively input to a first adder and a second adder to provide first and second sums. The first and second sums are output from a first and a second storage device for feedback input respectively to the first and second adder to provide the first and second sums. A carry bit output from the second storage device is generated responsive to each wrap condition associated with the storing of the second sums in the second storage device. The carry bit is fed back to the first adder and fed forward for subsequent consolidation with the first sums respectively output from the first storage device. The first sums and the second sums are respectively accumulated as numbers represented in a redundant number system.

Abstract: Phase-to-sinusoid conversion and method for direct digital synthesis are described. At least one quadrant of values for a sinusoidal signal are real-to-finite bit resolution mapped to provide preconditioned values which are on average shifted down by half of a LSB position. The at least one quadrant of preconditioned values are stored in a lookup table. MSBs of a phase-accumulated signal are used as an address for accessing from the lookup table a sinusoid value. At least a logic 1 is added as an LSB to an interim output associated with the sinusoid value to provide an adjusted sinusoid value having a bit width greater than that of the sinusoid value to provide a digitally synthesized sinusoidal value.

Abstract: In the field of optical communications, the need to remove jitter from a Synchronous Digital Hierarchy (SDH) or Synchronous Optical NETwork (SONET) datastream is recognized. Consequently, the present invention provides a First-In-First-Out (FIFO) buffer having a read-out clock frequency that is controlled in response to a depth error of the FIFO buffer. The control of the read-out clock frequency is achieved by a hardware control loop coupled to the FIFO buffer. The period of the control loop is a product of the frequency at which the depth error of the FIFO buffer is acquired and another factor. The another factor is the number of states of logic employed by the control loop raised to an integer power.

Abstract: For testing communication in a network which carries data frames between communications ports having respective addresses, each frame containing an indication of the address of the source of the frame, the address of the intended destination of the frame, and other data, a tester has at least one communications port and a receiver for receiving a data frame arriving at the communications port. The tester includes circuitry for recognising test data frames according to at least one predetermined criterion, and extracting predetermined items from each test data frame including the source and destination addresses. A new test data frame is generated incorporating the predetermined items, with the source and destination addresses exchanged, and incorporating additional content of predetermined value, and a transmitter transmits the new data frame with the exchanged addresses into the network.

Abstract: In the field of optical communications, the need to remove jitter from a Synchronous Digital Hierarchy (SDH) or Synchronous Optical NETwork (SONET) datastream is recognized. Consequently, the present invention provides a First-In-First-Out (FIFO) buffer having a read-out clock frequency that is controlled in response to a depth error of the FIFO buffer. The control of the read-out clock frequency is achieved by a hardware control loop coupled to the FIFO buffer. The period of the control loop is a product of the frequency at which the depth error of the FIFO buffer is acquired and another factor. The another factor is the number of states of logic employed by the control loop raised to an integer power.

Abstract: A tester for testing communication links in a network which carries data frames between communications ports having respective station addresses includes a plurality of communications ports and a test data generator for generating test data frames to be transmitted via the communications ports. A store holds a plurality of sets of predefined station addresses to be associated with the communications ports. A selector receives an indication of user selection of one of a plurality of test modes of the tester, and selects in accordance with that indication a respective one of the sets of predefined station addresses for association with the communications ports. The selector may also receive an indication of user selection of one of several test modes, and select a respective mode of operation of the communications ports and of the test data generator.