基于NXP ARM微控制器的以太网吞吐量
本文提出了一种测量以太网吞吐量的方法,提供了良好的性能估计,并说明了影响性能的各种因素。
以太网是世界上应用最广泛的局域网(LAN)技术。它从80年代初开始使用,并被IEEE STD 802.3所覆盖,它指定了许多速度等级。在嵌入式系统中,最常用的格式是10 Mbps和100 Mbps(通常称为10/100以太网)。
有超过20的NXP ARM MCU内置以太网,涵盖所有三代(ARM7、ARM9、ARM的Cortex-M3)。恩智浦使用基本相同的实现跨越三代,使设计人员可以利用他们的以太网功能,当系统进入ARM的下一代节省时间和资源。
本文讨论了三种不同的情况下测量以太网吞吐量的LPC1700产品和细节,真正实现了优化系统。
Superior implementation
NXP‘s Ethernet block (see Figure 1) contains a full-featured 10/100 Ethernet MAC (media access controller) which uses DMA hardware acceleration to increase performance. The MAC is fully compliant with IEEE Std 802.3 and interfaces with an off-chip Ethernet PHY (physical layer) using the Media Independent Interface (MII) or Reduced MII (RMII) protocol along with the on-chip MII Management (MIIM) serial bus.
The NXP Ethernet block is distinguished by the following:
Full Ethernet functionality — The block supports full Ethernet operation, as specified in the 802.3 standard.
Enhanced architecture — NXP has enhanced the architecture with several additional features including receive filtering, automatic collision back-off and frame retransmission, and power management via clock switching.
DMA hardware acceleration — The block has two DMA managers, one each for transmit and receive. Automatic frame transmission and reception with Scatter-Gather DMA offloads the CPU even further.
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