US 6,208,667 B1 · Constant phase crossbar switch

Abstract

A constant phase crossbar switch system which avoids phase discontinuities at the outputs of the crossbar switch. The crossbar switch system includes input logic, a crossbar switch, output logic and a phase locked loop. The phase locked loop is used to generate a high speed internal clock from a system clock. High speed serial data streams transmitted at the internal clock frequency are received from corresponding transmitters and are coupled to the input logic. The input logic generates multiple versions of each serial data stream, one of the versions being undelayed and the other versions delayed by some fraction of a bit time. State machines are employed to selects the version of the serial data stream which results in the data stream data window being generally centered with respect to the high speed internal clock. The selected version of the data stream is employed as the active input to the crossbar switch. The selected version of each of the data stream is clocked into an output register which is clocked by the internal clock. The selection of the phase delayed version of the serial data stream in the described manner avoids phase discontinuities upon switching of sourcing transmitters.

Claims9

Dependent claims

A constant phase crossbar switch system having a plurality of switch system inputs and outputs, comprising:

a crossbar switch having a plurality of inputs and a plurality of outputs, said crossbar switch being operative to selectively couple a serial data stream appearing on at least one of said plurality inputs to at least one of said outputs, wherein said serial data stream is clocked at a predetermined frequency;
at least one input logic circuit, said at least one input logic circuit having an input for receiving a serial data stream from a corresponding transmitter transmitting said data stream at a specified frequency for receipt at one of said switch system inputs, said input logic circuit also having an output in electrical communication with one of said inputs of said crossbar switch, said at least one input logic circuit receiving as an input an internal clock having a clocking edge and running at said specified frequency, said at least one input logic circuit including a multitap delay line having an input and a plurality of delay line outputs, said serial data stream being coupled to said input of said multitap delay line, said multitap delay line being operative to generate increasingly delayed versions of said serial data stream at successive ones of said delay line outputs, said input logic circuit being operative to select a delayed version of said serial data stream from one of the delay line outputs for application to said one input of said crossbar switch.

A method of transferring a serial data stream from a transmitter to a receiver in a crossbar switch, the transmitter and receiver both employing an internal clock to accomplish the data transfer, the method comprising the steps of:

during an alignment operation, performing the steps of:
(i) transmitting a predetermined alignment pattern in the serial data stream;
(ii) generating a plurality of phase-delayed replicas of the serial data stream;
(iii) sampling each phase-delayed replica of the serial data stream with the internal clock over a plurality of cycles of the predetermined pattern;
(iv) monitoring the sequences of samples of the phase-delayed replicas to indicate for each sequence whether the predetermined pattern is correctly detected therein throughout the plurality of cycles of sampling;
and
(v) based on the indications for each sampled sequence, selecting one of the phase-delayed replicas of the data stream to be transmitted to the receiver, the selected replica being the replica having a data valid window most centered on the clocking edge of the internal clock;
and
subsequent to the alignment operation, transmitting the selected phase-delayed replica from the transmitter to the receiver.

6 more elements

Dependencies are inferred from the claim text.

Constant phase crossbar switch

Life of this patent

Constant phase crossbar switch

Life of this patent

Abstract

Claims9