Abstract: In this article, the microprocessor LPC2368 basic DP83848C Ethernet physical layer chip, detailed description of the method of implementing integrated Ethernet interface. LPC2368 microprocessor and the first physical layer chip DP83848C briefly presented, then given based on LPC2368 for the design of equipment Ethernet interface, the document describes the process of implementing software. 1 Introduction With the rapid development of Internet technology, sharing information on demand is also rising. Currently, embedded systems have penetrated every corner of our lives is the perfect combination with the network of information sharing that we offer a great convenience. Philips is a good company LPC2368 microprocessors, embedded systems based on its Ethernet interface, otherwise the application will also greatly reduced. Thus, the entire system, the Ethernet interface circuit must be indispensable, but it is also relatively complex. Ethernet interface circuit mainly from the MAC controller and interface physical layer (PhysicalLayer, PHY), two major parts. LPC2368 integrated Ethernet controller, support for the rationalization of the interface (the Independent Media Independent Interface ReducedMedia, RMII) and the DMA buffer interface (Buffered DMAInterface BDI), half-duplex and full duplex mode, providing 10M/100Mbps of Ethernet access. Therefore, LPC2368 internal fact already includes Ethernet MAC control, but did not provide a physical layer interface, therefore, necessary to add an Ethernet physical layer chip to provide the access channel. Here use DP83848C NationalSemiconductor as Ethernet interface physical layer circuit, which provides, including MII / RMII / SNI interface can be easily connected with the LPC2368. 2 LPC2368 And DP83848C Introduction 2. A microprocessor LPC2368 LPC2368 ARM7TDMI-S 32 heart-bit based microcontroller can operate up to 72 MHz frequency, its powerful and profitable 10/100Ethernet support, full speed (12Mbps) USB 2. 0 and CAN2. 0B; chip with up to 512KB Flash, 58KB SRAM, 10 A / D and D / A converter and an oscillator IRC, also interfaces with an SD memory card are available, 100-pin LQFP package (14 × 14 × 1. 4mm). Widely used in industrial control, protocol conversion POS systems, encryption and other areas [1]. 2. 2 physical layer chip DP83848CDP83848C 10/100Mb/s a unipolar low-power physical layer devices, there are several power-down mode Intelligent, including a 25MHz clock output, it is easy to twisted pair media via a transformer external interfaces; supports two IEEE802. MII and RMII 3U Rev1. 2, convenient design, integrated sub-layer supports 10BASE-T and 100BASE-TX Ethernet protocol, low power consumption less than 270mW, 3. 3VMAC interface, the interface can configure NIS, 48-pin LQFP package quoted (7x7mm). DP83848C as Ethernet transceiver physical layer, widely used in high-end devices, industrial control and factory automation, general-purpose embedded applications [2]. 3 Design of equipment 3. 1 Circuit Diagram LPC2368 related DP83848C relatively simple, can be directly via the RMII interface. Once connected, the network DP83848C isolation transformer and RJ45 interface to access the transmission medium, the diagram of Figure 1. 3. 2 Design of Ethernet interface circuit real schémaDP83848C supports multiple MAC interface: (1) ITN, (2), RMII (ReducedMII) (3) 10 MB network interface serial (Serial NetworkInterface, SNI) . Here, we use the RMII interface mode, by setting the Pin pin39 pin6 and determine, as indicated in Table 1. Table 1: Selecting ITN MII_MODE (pin39) SNI_MODE (pin6) MAC interface mode0 0 or 1 1 0 RMII MII Mode Mode 1 1 10 Mb SNI mode can be seen in Table 1, pin39 should be connected to senior pin6 must be connected to depression. At the same time, because the chip pin6 box, the default is 0, so that you can set the pin39 connected to the high level, so that the microprocessor can LPC2368 PHY DP83848C with chip connected via RMII interfaces. Between them via the RMII interface, the chip and controller pins used to connect the number of relatively small, and the rate of data transfer both, or frequency of 50MHz, requires a 50MHz crystal oscillator connected to pin34X1 feet. In RMII mode, the main use of the pin: 1 Serial Management: MDC (pin31), MDIO (pin30); 2M data: TX_EN (pin2), TXD [1:00] (pin4pin3) RX_ER (pin41) , CRS_DV (pin40), RXD [1:00] (pin44pin43) 3 Clock: X1 (pin34, RMII reference clock is 50MHz), X2 (pin33). Pin27 home DP83848C to 100Mbps high rate of work, the LED Show DP83848C condition. 16ST8515 transformer isolation network, the main signal transmission, impedance matching, repair wavelength, removing clutter and the role of high voltage isolation to protect the security of the system . By protel99 SE circuit diagram drawn in Figure 2. Software for the achievement of three main parts: the system initialization, the data sent and reçues.partie initialization of the Ethernet interface in use before the completion of initialization, including the provision of the relevant register allocation and initialization to send and receive buffers. Network Interface layer in the corresponding data packet is a full Ethernet frame format, and thus the sending and receiving data must be carried out according to the Ethernet IEEE802. 3 of the Protocol, the protocol frame structure as defined in Table 2. Each card in the factory when there is a global fixed physical address (MAC address). When the bus node sends a data frame, the bus on the nodes of the network are more copies of the data frame, each node check