Analysis of the design and implementation of Soho router

O Introduction

As the core equipment of the Internet, the router market is also more and more wide. The growing popularity of the network to homes and offices has driven the needs of small routers, the Soho router. Now, there has been a large number of Soho-oriented network communications products on the market. The ARM9 series microprocessor is the first choice of router configuration for its superior performance, low price and mature technology. Based on ARM9 core chip and Uclinux operating system development model, this paper introduces the design and technology implementation of a Soho router in detail.

1 SOH0 Router Design idea

The road south is an embedded device, which can not be separated from the support of hardware and software systems, and its development is generally understood as a three-tier model: hardware devices, operating systems, and applications running on the operating system. Hardware equipment is mainly composed of microprocessor and component circuit around microprocessor chip, it is the hardware foundation of device function realization; the middle tier is the operating system, which connects hardware parts and applications, operating systems that perform basic operations on the underlying hardware and provide operational environment support for applications , the operating system is the application, is responsible for implementing targeted application of the program code, corresponding to the router's network architecture and communication protocols and other functional modules.

2 Hardware Implementation

The hardware structure of the SOH0 router is shown in Figure 1. The core of the figure is a 88E6218 high-performance 16/32-bit microprocessor produced by the American Marvell Company. The chip is specifically designed for SOHO routers and Ethernet switches, relative to the current market for network communications processors. 88E6218 has the advantages of high performance and low cost. In addition, the processor has a DSP-extended arm946e high-performance CPU core operating at 133/150 MHz with a 16/32-bit RISC system with 8 KB instruction cache, 8 KB data cache, and 8 KB data RAM, can support Uclinux and Vxwork operating system memory management, and built-in 32-bit ARM instruction system and 16-bit instruction set.

88E6218 has integrated Ethernet interface and switching function, it has a UNIMAC structure inside, it can realize Fast Ethernet switching function based on QoS mechanism. Its structure diagram is shown in Figure 2. 88E6218 Chip has 5 support IEEE802. 3 Adaptive Ethernet interface and MAC address port, which includes 4 10/100base-tx LAN ports and one 10/100BA-SE-TX or 100base-fx selectable mode WAN port. These ports support 802-mode network protocols for various routes, as well as 10/100 Mbps two transmission rates and full/Half-duplex transport capabilities. Each port has CRC parity, judgment, and transfer functions, and has packet buffer memory on the chip, and is in line with IEEE 802. 3ab,802. 3x,802. p,802. -1q the standard management function. In addition, the device also has IEEE 802. 1p flow priority sequence capability, available in IEEE 802. 1Q Valn function and can be switched without blocking.

The peripheral function module of 88E6218 chip includes Sdram/flash controller, JTAG interface, programmable universal I/O port, UART serial interface, interrupt controller, storage controller and power adjustment PIN, etc. In addition, 88E6218 also has an important feature is to provide the PHY LED lamp controller, can be used to indicate whether the Port transceiver connection, receive, send, Full-duplex and other working conditions to determine the network through the LED Display connection status.

In the Soho router shown in Figure 1, the core processor chooses 88E6218. The chip provides 4 LNA ports, which can be connected to 10/100m Ethernet, another WAN port to the WAN, and each port has Exchange function. According to the operating system storage and operation needs, the chip also set up SDRAM memory and flash memory, SDRAM memory by a 4x2 Mxl6 B hy57v281620 composition, is operating system, application running and some data cache space. The flash memory consists of a 512kx8bit am29lv040b that holds the B00tleader files, operating systems, and applications of the boot program binaries. The 20-pin arm JTAG port is used to debug the program and burn the Flash. The RS232 interface is used to provide configuration management functionality and to reflect information operation. The clock circuit consists of a MHz crystal oscillator and a filter capacitor, and the Resert circuit consists of a DSL708TESA chip plus a manual press twist to form a low electric calming bit. Power supply circuit input of 5 V, through DC transformer, can be adjusted under the power supply adjustment pins under the pressure to provide 1. 5 V, 1. V, 2. 5V, 3. 3 v voltage to the processing chip for the chip to work smoothly. In addition, the circuit also has a large number of filter and voltage regulator capacitor. In order to allow users to clearly understand the working state of the router, the system is connected with the LED indicator, which can be used to determine the connection status and working status of the SOH0 router.