High Speed Packet Interface Multi-Lane Flow Control
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Solution Overview
Problem
XAUI interfaces lack channelization and flow control features necessary for multi-channel packet transmission, limiting their effectiveness in chip-to-chip communication.
Innovation Solution
The High Speed Packet Interface (HSPI) method and interface architecture enable multi-channel packet transmission over XAUI and similar serial interfaces by fragmenting packets into meta-frames with embedded flow control information, using 64b/66b encoding, and maintaining lane alignment and clock compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a parallel interface like SPI4.2 is used, then channelization and per-channel flow control are achieved, but the interface width becomes very large (more than 80 I/Os) and reach is limited to about a dozen inches
Solution Approach 1:
The patent segments the parallel interface functionality into multiple serial lanes, where each lane carries a portion of the data. This allows the system to achieve multi-channel capability through time-division multiplexing across serial lanes rather than requiring a wide parallel interface, thereby extending reach while maintaining channelization.
Solution Approach 2:
The patent transitions from a spatial dimension (wide parallel interface with many simultaneous I/Os) to a temporal dimension (narrow serial interface with time-multiplexed channels). By encoding multiple channels sequentially over time on fewer physical lanes, the system achieves channelization without requiring excessive I/O width, enabling longer transmission distances.
2Length of stationary object
If a serial interface like XAUI is used, then longer range and routing capability are achieved, but channelization and flow control features are lost
Solution Approach 1:
The patent introduces dynamic channel allocation and flow control mechanisms on top of the static XAUI serial interface. By dynamically assigning different channels to different time slots and implementing per-channel flow control through control words embedded in the data stream, the system gains adaptability and channelization capabilities while maintaining the long-range benefits of serial transmission.
Solution Approach 2:
The patent makes the serial interface universal by designing a protocol that can carry multiple channels, flow control information, and data of varying priorities all over the same physical medium. The interface can adapt to different channel configurations and flow control requirements without changing the underlying physical layer, achieving multi-functionality on a single serial connection.
3Adaptability or versatility
If packet fragmentation into meta-frames is implemented, then multi-channel transmission with flow control is enabled, but frame structure complexity increases
Solution Approach 1:
The patent introduces meta-frames as an intermediary structure between the physical serial interface and the logical packet data. The meta-frame format includes control words that mediate channel identification, flow control signaling, and data segmentation. This intermediary structure organizes the complexity into a standardized format that simplifies processing compared to ad-hoc multi-channel implementations.
Solution Approach 2:
The patent changes the framing parameters from traditional packet-based structures to meta-frame structures with fixed sizes and embedded control information. By standardizing the meta-frame format with defined field lengths and control word positions, the system reduces processing complexity despite adding multi-channel capability, as the fixed structure enables efficient parsing and handling.
Data Source
AI summary
A high speed multi-lane serial interface and method for constructing frames for such an interface are provided. Frames are constructed for transmission on a multi-lane serial interface. For each of a plurality of transmit channels, packets are fragmented into fragments. Meta-frames are generated having a size defined by a constant meta-frame length×number of lanes, each frame having a meta-frame separator and a payload. Per-transmit channel flow control information is received. Each payload has a plurality of bursts, each burst comprising a burst control word and an associated data burst, the burst control word identifying one of said transmit channels to be transmitted on the associated data burst, each data burst comprising one of the fragments for the transmit channel identified in the associated burst control word. The channels to transmit in a given meta-frame are selected as a function of the received flow control information.