0. introduction
In recent years, in-vehicle and portable multimedia playback devices have been highly sought after by people, competing to launch a variety of design solutions. The design solutions of in-vehicle and portable devices based on the Loongson 2F [1, 2] (LOONGSON-2F) processor are mainly oriented to high-performance, low-power embedded fields such as in-vehicle entertainment, ultra-mobile devices (UMD), mobile Internet devices (MID), etc. Companies engaged in development and production. The solution uses the Loongson 2F (LOONGSON-2F) processor as the control core. According to the working environment and characteristics of the vehicle and portable equipment, the SM502 [3] multi-function display control chip is used. It can support multiple media formats and can realize Internet access and viewing. TV, recording and playing music and other functions; onboard FLASH and DDR2 memory, can independently guide the system kernel to work, using the serial port as the system terminal. The system can also be expanded through the onboard universal PCI and LOCAL BUS total route interface, which is convenient for users to carry out secondary development. In addition, the CPU uses domestic chips, which has the characteristics of low power consumption and low price. This design scheme has high application and reference. value.
1. Loongson 2F processor functions and features
The Loongson 2F (LOONGSON-2F) processor used in this system is a 64-bit MIPS III instruction set general-purpose RISC microprocessor newly released by the Institute of Computing Technology, Chinese Academy of Sciences. The processor adopts the 90nmCMOS design process for the first time in China, with an area of ​​35nm2, a measured power consumption of 4 ~ 5W at a typical operating frequency of 800MHz, and a maximum operating frequency of 1G; the highest floating-point operation speed is 4/8 billion times per second Double / single precision floating point operation, integrated IO controllers such as PCI / PCIX, and integrated on-chip secondary CACHE, DDR2 memory controller, very suitable for high-end embedded field.
2. The structural framework of the system hardware structure design system is shown in Figure 1.
The Loongson 2F (LOONGSON-2F) processor is the control center of the entire system and undertakes all data processing tasks. The system uses the ICS950220 clock synthesizer to generate the clock required by each chip on the motherboard, and the chip has a watchdog function. The system memory is expanded by the DDR2 controller integrated in the processor. Considering the area of ​​the PCB printed board and the higher bandwidth requirements for memory access, 4 16-bit memory granules are used. The memory capacity depends on the capacity of the granules. , Maximum support 1GB memory, its working frequency is 300MHz. The LOCAL BUS extended 512KB Flash ROM provided by the processor is used for system BIOS storage.
2.1 System power
Whether it is a car or a portable device, it needs to be powered by a DC power supply. Therefore, energy saving and high efficiency are the subjects of power supply design. As can be seen from the power module in Figure 1, the system motherboard uses a + 5V DC adapter as the power supply. The 1.2V power supply used by the CPU and the 3.3V DC power supply used by the interface circuit are both more efficient due to the higher current passing. Switching power supply. According to the conventional design, the 1.8V power supply for DDR2 and SM502 is introduced from the 3.3V power supply, which is generated by two linear power supplies (LDOs). The system is changed to a higher-efficiency switching power supply, which improves the efficiency of the entire system. The actual power consumption of the whole system is controlled within 10W.
2 System interface
1. The system drives various interfaces through the multi-function display control chip SM502. The SM502 can be directly connected to the processor through PCI BUS and supports 2D display acceleration. It can provide: AC97 standard audio interface (controlled by ALC203 chip), a UBS1.1 interface , A standard RS232 serial port and a debug serial port (all controlled by SP3232 chip), VGA and LCD display interface, ZV video interface (controlled by SSA7118 chip).
2. The system adopts RTL8139D as the Ethernet control chip through PCI BUS and provides 10 / 100M Ethernet interface. 3. The system uses uPD720102 as the USB controller chip through PCI BUS, and provides three USB2.0 interfaces. One of the USB ports provides an SD / MMC interface through the AU6331 card reader controller chip.
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