3com Corporation

Lai-Chin Lo

David R Brown

Brian A Petersen

W Paul Sherer

Ngo Thanh Ho

Chi-Lie Wang

John F Hickey

William Paul Sherer

Nathaniel H Henderson

Krishna Uppunda

A transmit packet buffer (TPB) is used on a network interface card (NIC) to store downloaded packets and forward them through the media access controller (MAC) and the physical layer interface (PHY) onto the wire. A multi-function TPB is implemented to allow the multiple usage of this buffer. Packets may be downloaded to this buffer through multiple sources. Different types of the packets may each be stored at predefined locations. For example, while the second half of the TPB is used to transmit keep-alive or alert-on-LAN packets, the first half may be used to compare received packets with a wake-up pattern for system wake-up. With multi-function support, various PC management functions may be implemented more effectively and with reduced cost.

Multi-function transmit packet buffer

An asynchronous switching circuit for multiple indeterminate bursting clocks. In one embodiment, the present invention recites a clock-switching circuit that provides a single unclipped and glitch-free clock signal at its output from among multiple clock inputs. The clock-switching circuit is comprised of a plurality of asynchronously-enabled clock circuits, a plurality of blocking circuits, a synchronizing clock, and a logic gate. Each of the plurality of blocking circuits has an input lead respectively coupled to one of the plurality of asynchronously-enabled clock circuits, each of the plurality of blocking circuits also has an output coupled to all of the plurality of asynchronously-enabled clock circuits except the one to which its input is coupled. The synchronizing clock is coupled to each of the plurality of blocking circuits while the logic gate is coupled to each of the plurality of asynchronously-enabled clock circuits.

Asynchronous switching circuit for multiple indeterminate bursting clocks

An Ethernet network or other CSMA/CD network includes hub adaptors that are modified to provide a known bounded low maximum access latency. The modified adaptors maintain a state variable whose values indicates whether the last operation by the adaptor was a transmit or a receive. In the case where the last operation was a receive, the adaptor transmits a packet with a minimum or zero backoff and as an option with a reduced interpacket gap. In the case where the last operation was a transmit, the adaptor waits before transmitting a packet a period of time that allows the other node on the channel to transmit a packet if the other node has a packet to transmit.

Method and apparatus for controlling latency and jitter in a local area

A data path aligner transfers data from an input having N byte lanes with byte enable bits to an output having N byte lanes. The aligner includes first stage having N-1 selector/registers, and a second stage having N selector/registers. Each of the N-1 selector/registers S1(i) in the first stage has inputs including input lanes L(j) for j going from i+1 to N. Each of the selector/registers S2(i) in the second stage has inputs including input lanes L(k) for k going from i to 0, and for selector/registers S2(i) for i less than or equal to N-2, the inputs include the output of a first stage selector/register S1(i). The outputs of the second stage selector/registers supply data selected from the respective inputs to output segment lanes. All of these selector/registers are controlled by a common select signal derived from a data path offset, and all selector/registers are clocked by a common clock.

DMA data path aligner and network adaptor utilizing same

Combined indication signals of data block transfers are generated by a device which reduces the number of interrupts to a host processor. The reduction in the number of interrupts enhances host system performance during data block transfers. An embodiment of the device may be a network adapter comprising network interface logic for transferring a data frame between a network and a buffer memory and host interface logic for transferring a data frame between a buffer memory and a host system. The network adapter further includes threshold logic for generating an early receive indication signal when a portion of the data frame is received. Indication combination logic delays the generation of a transfer complete interrupt to slightly before the expected occurrence of the early receive indication. The host processor is able to service both the transfer complete indication and the early receive indication in a single interrupt service routine caused by the transfer complete indication.

Device with host indication combination

Optimized indication signals of a completed data frame transfer are generated by a network adapter which reduces host processor interrupt latency. The network adapter comprises network interface logic for transferring the data frame between the network and a buffer memory and host interface logic for transferring the data frame between the buffer memory and the host system. The network adapter further includes threshold logic where a threshold value in an alterable storage location is compared to a data transfer counter in order to generate an early indication signal. The early indication signal may be used to generate an early interrupt signal to a host processor before a transfer of a data frame is completed. The network adapter also posts status information status registers which may be used by the host processor to tune the timing of the generation of the network adapter interrupt signal.

Network adapter with host indication optimization

A network interface controller controls communication between a host system and a network transceiver coupled to a network comprises a memory outside of the host address space in which receive and transmit buffers are managed, host interface logic emulating memory mapped registers in the host address space, for transferring data between the host address space and the buffer memory, and network interface logic coupled with the network transceiver, for transferring data between the buffers in the buffer memory and the network transceiver. The buffer memory includes a transmit descriptor ring buffer, transmit data buffer, transfer descriptor buffer, and receive ring buffer all managed by operations transparent to the host.

Growing community of inventors

Campbell, CA, United States of America

Lai-Chin Lo