Crossbar switch and method with reduced voltage swing and no internal blocking data path

• US 5,991,296 A
• Filed: 02/22/1996
• Issued: 11/23/1999
• Est. Priority Date: 02/22/1996
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Larson, Jeffrey D., Mu, Albert
• Primary Examiner(s): NGUYEN, CHAU T
• Application Number:
  US08/604,920
• Time in Patent Office: 1,370 Days
• Field of Search: 370/380, 370/381, 370/352, 370/395, 370/412-416, 340/825.85, 340/825.9, 340/825.93, 340/825.89, 340/825.95, 365/208
• US Class Current: 370/380
• CPC Class Codes: H04L 49/101 using crossbar or matrix
• CPC Class Codes: H04L 49/205 Quality of Service based
• CPC Class Codes: H04L 49/25 Routing or path finding in a switch fabric
• CPC Class Codes: H04L 49/254 Centralised controller, i.e. arbitration or scheduling
• CPC Class Codes: H04L 49/3018 Input queuing
• CPC Class Codes: H04Q 3/523 Details

Abstract

A switch system and method transfer a data packet from a source data port to one or more destination data ports through a switch. The system comprises a source input buffer, a first and a second source input path, a first and a second output path and at least one crosspoint circuit. The source input buffer includes a first and a second data section. The first and the second data sections are coupled to the first and the second input paths respectively. The first and the second input paths couple through the crosspoint circuits at each intersection with the first and the second output paths. The method includes loading the data packets into data sections of an input buffer, transferring each data packet across an input path dedicated for each data section, transmitting each data packet over its input path, and switching the data from the input path to the output path based on a voltage differential. A crosspoint circuit in the switch system includes a first and a second reduced voltage swing line, a first and a second transistor circuit for each data input path and a sense amplifier for a data port. The first reduced voltage swing line is coupled to the first transistor circuit, the second reduced voltage swing line is coupled to the second transistor circuit and both reduced voltage swing lines are connected to the sense amplifier. The method of the unit comprises the steps of charging a first and a second reduced voltage swing line to a predetermined voltage, discharging the voltage from the first reduced voltage swing line, maintaining the voltage in the second voltage line, receiving a clock signal at the sense amplifier, and generating an output signal based on a voltage differential between the voltage lines.

Claims

1. A switching system for selectively transferring data packets and including a switch, an input buffer having a first data section and a second data section, and a destination data port, the system comprising:

a first dedicated input path coupled to the first data section and a second dedicated input path coupled to the second data section, the first dedicated input path and the second dedicated input path for transferring data packets from the first data section and the second data section, respectively, to the switch;

an output path coupled to the destination data port for transmitting the data packets to the destination data port; and

a first reduced voltage swing crosspoint circuit, disposed in the switch, to couple the first dedicated input path and the output path, and a second reduced voltage swing crosspoint circuit, disposed in the switch, to couple the second dedicated input path and the output path, the first reduced voltage swing crosspoint circuit and the second reduced voltage swing crosspoint circuit for switching the data packets from the first dedicated input path and the second dedicated input path, respectively, to the output path,

wherein each reduced voltage swing crosspoint circuit generates a differential signal, and includes a precharge circuit that is switchable to an off state prior to a discharging of the reduced voltage swing crosspoint circuit.

2. The switching system as in claim 1, wherein each reduced voltage swing crosspoint circuit further comprises a sense amplifier for producing a full-swing output signal, the sense amplifier having a differential input for receiving the differential signal generated by the reduced voltage swing crosspoint circuit.

3. The switching system as in claim 1, further comprising an arbitration unit for determining whether the destination data port is available to receive the data packet, the arbitration unit coupled to the switch.

4. The switching system as in claim 1, wherein the switching system further comprises switching circuit signals.

5. In a switching system for selectively transferring data packets and including a switch, a plurality of output paths, and an input buffer having a plurality of data sections, each data section coupled to a dedicated input path, a method for transferring data comprising the steps of:

loading a plurality of data packets into the plurality of data sections;

transferring each data packet to the switch over each dedicated input path coupled to each data section holding each data packet; and

switching each data packet from each dedicated input path to an output path through a reduced voltage swing crosspoint circuit,

wherein the reduced voltage swing crosspoint circuit generates a differential signal, and includes a precharge circuit that is switchable to an off state prior to a discharging of the reduced voltage swing crosspoint circuit.

6. The method as in claim 5, further comprising the step of coupling each dedicated input path to the switch.

7. The method as in claim 5, wherein the switching step further comprises the step of electrically coupling a dedicated input path and an output path.

8. The method as in claim 5, further comprising the step of determining whether a destination data port is available to receive a data packet.