## Overview of the PLX/Broadcom NET2280 The **NET2280** is a high-speed USB 2.0 peripheral controller designed by PLX Technology (now part of Broadcom). It is primarily used to bridge a local bus (such as a processor or FPGA) to a USB 2.0 interface. --- ### 1. Core Hardware Specifications The NET2280 is designed for high-bandwidth applications. Below are its primary technical specifications: | Feature | Specification | | :--- | :--- | | **USB Version** | USB 2.0 High-Speed (480 Mbps) | | **Local Bus Interface** | 32-bit, 33MHz PCI-like asynchronous interface | | **FIFO Memory** | 8 KB of internal RAM for buffering | | **Endpoints** | 4 Configurable Endpoints (plus Endpoint 0) | | **Voltage** | 3.3V I/O with 1.8V Core (Internal regulator included) | | **Package** | 120-pin TQFP or 176-pin Fine Pitch BGA | --- ### 2. Key Electronic Subsystems #### A. The PCI-like Local Bus The NET2280 does not connect directly to a CPU via SPI or I2C. Instead, it uses a **32-bit asynchronous local bus**. This allows it to interface with: * FPGAs (Xilinx, Intel/Altera) * High-end Microcontrollers * DSP (Digital Signal Processors) #### B. DMA Engine One of the most critical electronic parts of the NET2280 is its **Direct Memory Access (DMA)** controller. It supports: * **Scatter-Gather DMA:** Allows the chip to read/write data from non-contiguous memory locations without CPU intervention. * **High Throughput:** It can saturate the USB 2.0 bandwidth (up to 40 MB/s actual throughput). #### C. PHY and Transceiver The chip integrates the **USB Physical Layer (PHY)**. This means the electronics for managing differential signaling ($D+$ and $D-$), impedance matching, and high-speed handshaking are built directly into the silicon, requiring minimal external components (usually just a crystal and a few resistors/capacitors). --- ### 3. Pinout and Connectivity Categories The pins on the NET2280 are generally grouped into three functional areas: 1. **USB Interface:** $D+$, $D-$, and $V_{BUS}$ sensing. 2. **Local Bus Interface:** Address lines ($A1-A10$), Data lines ($D0-D31$), and control signals ($RD\#, WR\#, CS\#$). 3. **Power and Clock:** $30MHz$ crystal oscillator inputs and decoupled power pins for the internal $1.8V$ core. --- ### 4. Typical Application Circuit In a standard electronic design, the NET2280 acts as the "USB Port" for a larger system: ```mermaid graph LR A[FPGA / Microprocessor] -- 32-bit Data Bus --> B[NET2280 Controller] B -- USB D+/D- Lines --> C[USB Type-B Connector] D[30MHz Crystal] --> B ``` --- ### 5. Summary of Benefits * **Low CPU Overhead:** The internal DMA and large FIFO buffers handle the "heavy lifting" of USB protocols. * **Flexibility:** Can be configured to act as various USB classes (Mass Storage, CDC, Custom HID). * **Legacy Support:** Though older, it remains a standard for industrial equipment requiring stable USB 2.0 connectivity.