International Business Machines Corporation

International Business Corporation

Patrick J Jeanniot

Alain R Blanc

Jean-Claude Abbiate

Gerard Richter

Bernard Brezzo

Pierre Debord

Gerard Orengo

Alain Saurel

Eric Lallemand

Robert L Leotard

Sylvie Spalmacin-Roma

Alain Pinzaglia

A method and systems for automatically adjusting the parameters of signal emitter in a synchronous high-speed transmission system, is disclosed. According to the method of the invention, the quality of a high-speed received signal is analyzed for a plurality of sets of parameter values and the one producing the best signal quality is selected. In a first embodiment, the quality of the high-speed received signal is determined by analyzing a digital eye characterizing the signal behavior, obtained by over-sampling the high-speed received signal. In a second embodiment, the quality of the high-speed received signal is determined by analyzing the behavior of the phase rotator used for data sampling. Finally, in a third embodiment, the quality of the high-speed received signal is determined by analyzing a digital eye, obtained by moving the position of a phase rotator from one end to the other and sampling data at each position.

Optimizing high speed signal transmission

Methods and systems for analyzing the quality of high-speed signals are provided, wherein a high speed signal is sampled simultaneously a plurality of times during a sampling clock period at each of a plurality of phase rotator positions to generate a plurality of partial values, wherein subset pluralities of the partial values are associated to phase rotator positions. The partial values are combined into a global value which is analyzed to determine a quality of the high speed signal. Phase rotator behavior may also be analyzed to determine signal quality. A best position to lock a phase rotator when determining signal quality may be determined from a graphic characterization of a phase rotator position distribution.

Method and systems for analyzing the quality of high-speed signals

Method and systems for optimizing high-speed signal transmission

A method and systems for analyzing the quality of high-speed signals, when signals can not be over-sampled due to sampler clock rates, is disclosed. According to the method of the invention, the position of a phase rotator is moved from one end to the other and data are sampled at each position (). Then, data are formatted () to obtain a global value characterizing the signal behavior. Finally, this global value is corrected () to remove signal transition falsely detected too early. The use of the phase rotator multiplies artificially the number of sampling positions.

A system for checking the integrity of data transfer in a switching element in a high speed packet switching network node where multicasting is performed by simultaneously shifting data from a first shift register into the targeted device shift registers. The outputs of the device registers are fed back into the first shift register. The checking system includes a device select circuit for selecting the targeted via a set of select lines and a negative OR gate circuit. The select line signals and the first register output are inputs to the OR gate, the output of which is fed back to the first register. A comparator circuit has inputs supplied by the device select lines and the outputs of the device registers. A processor compares the contents of the first register to the outputs from the logic comparator circuit to test whether the data has been properly multicast to the targeted.

System for checking data integrity in a high speed packet switching network node

A method and apparatus for managing contention in a self-routing switching architecture based on a set of n&times;n individual switching structures that are connected in a port expansion mode by means of fan-out and fan-in circuits providing access of the Switch Core Access Layer (SCAL) to the different input and output ports of the switching core. The fan-in circuits use an arbitration mechanism for providing a token to the switch that is allowed to deliver the next cell and the arbiter operates from a detection of a special comma character in accordance with the 8B/10B coding scheme which is introduced in the data flow between the individual switching structures and the fan-in circuits. This provides a compensation for the difference in transfer delays of the cells even when high switching speed and long length of the physical media are involved.

Method and apparatus for managing contention in a self-routing switching architecture in a port expansion mode

A Decimation filter for converting a train of sigma-delta pulses S(i) in synchronism with a sigma-delta clock (fs) into a train of Pulse Coded Modulation (PCM) samples in accordance with the formula ##EQU1## where Cn is the sequence of the coefficients of the decimation filter which corresponds to a determined decimation factor, and the PCM samples being processed by a Digital Signal Processor (DSP). The decimation filter includes a device for storing a digital value representative of the DC component introduced during the sigma-delta coding process, with the digital value being computing by the DSP processor during an initialization phase. The decimation filter further includes a device operating after the latter initialization phase for subtracting the stored digital value from each of the PCM samples so that the resulting sequence of PCM samples appears free of any DC component introduced during the sigma-delta coding. This accurate DC component suppression is achieved without necessitating the use of additional digital signal processor resources from the processor. Preferably, the decimation filter comprises a device for detecting a saturation occurring in the computing of the PCM sample, and responsive to the saturation detection, for transmitting a predetermined PCM sample to the DSP processor.

Decimation filter for a sigma-delta converter and A/D converter using

A decimation filter for converting a received train of sigma-delta pulses in synchronism with a sigma-delta clock (fs) into a train of Pulse Code Modulation (PCM) samples having a PCM clock in accordance with the formula ##EQU1## includes a computer for computing one PCM sample from a sequence of sigma-delta samples in synchronism with the PCM clock and also a comparison circuit for determining whether phase correction of the PCM clock is necessary to lock the generation of the PCM samples on the sigma-delta clock extracted from the received sigma-delta signal, the decimation filter including shifters which shift the computation process at least one sigma-delta clock pulse in order to provide phase control in the generation of the PCM samples.

Decimation filter for a sigma-delta converter and data circuit

A decimation filter for converting a train of sigma-delta pulses S(i) in synchronism with a sigma-delta clock (fs) into a train of PCM samples which includes counters (321, 331, 341) driven by the sigma-delta clock (fs) and which is continuously incremented by one during N sigma-delta clock pulses, then decremented by two during N following sigma-delta clock pulses and then incremented again by one during N following sigma-delta clock pulses in order to provide a sequence of incrementation parameter DELTA(n). The decimation filter further includes storages (320, 330, 340) for storing the value of the coefficient C(n) corresponding to the decimation filter transfer function, and incrementers (327, 337, 347) driven by the sigma-delta clock fs for incrementing the storages with the incrementation parameter DELTA(n). Finally, the decimation filter includes computers (323, 333, 343, 327, 337, 347) for deriving from the contents C(n) of said storages and from the train of input sigma-delta samples S(i+n) one Pulse Code Modulation (PCM) sample every 3.times.N input sigma-delta samples according to the formula: ##EQU1##

Decimation filter in a sigma-delta analog-to-digtal converter

A predictive clock extracting circuit having a first circuit for determining the duration between two consecutive transitions of a multilevel digital signal and a second circuit for generating an SPL pulse at half the duration after a third transition following on two consecutive previous transitions. A phase locked oscillator which is driven by said SPL pulse generates the extracted clock signal which is in phase with the SPL pulse and coincides with the center of the eye intervals of said multilevel digital signal. The system includes a first counter N which starts running in response to the detection of the first transition of the multilevel digital signal. The running stops when the second transition occurs. The result N(i) stored into the first counter N at second transition is therefore representative of the duration between the two consecutive first and second transitions. The preferred embodiment of the invention also involves an up/down counter K which generates a second counter K(i) that is expected to be representative of half the value of the first counter N(i). Counter K is adaptively updated by incrementing its current value K(i) by a fixed factor or, on the contrary, by decrementing its current value K(i) by a fixed damping factor.

Predictive clock recovery circuit

The data transmission system includes a data transmitter for transmitting either data bits or a sequence of N alarm bits in a first binary state. The transmitter includes a decode circuit (16) providing a detection signal each time that, in a data bit stream, a sequence of n bits in the first binary state has been loaded in a shift register (14), a XOR circuit (18) modifying the binary state of the bit following the sequence of n bits in response to the detection signal provided by the decode circuit (16), thereby providing a modified data bit stream on the transmit line (20), the number n being chosen so that no modified data bit stream can be formed of N bits in the first binary state which could be confused with the sequence of N alarm bits. On the reception side, the data receiver performs the reciprocal operation of the data transmitter.

Data transmission system with a digital alarm facility

A multiprocessor system includes a plurality of signal processors and a common unit processor. Each of the signal processors is connected to a different source of signals such as voice signals and performs one or more signal processing functions relative to the connected source. The common unit processor performs one or more functions for the signal processors on a shared synchronized basis. A signal processor adapter responsive to a source of clock pulses generates synchronous interrupts applied to the common unit processor and enabling signals in sequence to connect the signal processor in sequence to the common unit processor in synchronization with the interrupts. In addition, the signal processors are provided with ping-pong buffers at their inputs and outputs to enhance throughput.

Growing community of inventors

LaGaude, France

Patrick J Jeanniot