MCU implementation scheme of the hottest satellite

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MCU implementation scheme of satellite TV receiver control

stc001 is a high-performance and low-cost satellite TV receiver control chip. Different from the traditional ASIC implementation method, it realizes the relevant functions in the form of 8-bit MCU and software. Compared with ASIC, an obvious advantage is that it can realize various functions of the chip by modifying the software, which is suitable for the control of various analog satellite TV receivers

at present, some artists in developed countries in the world have long been tired of traditional means, and satellite TV has already entered their homes directly. The coverage of satellite TV users in some countries has exceeded 50%, and individual reception will become the mainstream of satellite TV reception. The biggest advantage of satellite live broadcasting is that it can broadcast hundreds of TV programs to an unlimited number of home users with only 1~2 satellites. China has a large population but uneven regional distribution, and cable TV is not developed, so it is the most suitable country to develop satellite TV live broadcasting. However, due to the influence of China's existing policies and the development level of satellite TV, China's satellite TV user coverage is far lower than that of developed countries in Europe and the United States. With the improvement of people's living standards, the purchasing power of consumers and the demand for watching satellite TV are getting higher and higher. Satellite TV will be a product with great development prospects. Therefore, as the core of satellite TV receiver, the control chip has a promising future

stc001 features

stc001 chip can receive control signals from the control panel and remote controller, and then control the satellite TV receiver to complete intelligent operations such as station selection, panel display, frequency modulation, tone modulation, signal polarization direction, etc. according to the received control signals. These intelligent operations are mainly realized by writing corresponding programs on the basis of embedded MCU. With the upgrading of products, you can also flexibly modify the code to achieve various new functions, which is the biggest advantage of embedding a RISC CPU in the chip. Considering the complexity of the functions to be realized by the satellite TV receiver control chip, the program space is set at 2KB

Figure 1: hardware structure diagram of stc001 chip

RISC is a milestone in modern computer architecture. The instruction set designed by RISC processor can be efficiently executed by pipeline processing and make the compiler produce optimized generation. The precision code required by flexible packaging can be achieved by adopting general lead screw and trapezoidal lead screw. Its characteristics are as follows: simple and unified instruction decoding; Most instructions can be executed in a single cycle; Only the load/store instruction accesses the memory; Simple addressing mode; Program jump delay. Based on these characteristics, RISC CPU can achieve the same performance with a much smaller circuit than the traditional CISC architecture, so it has the advantages of small area, fast speed and low power consumption

stc001 chip hardware structure is shown in Figure 1. The whole chip adopts 0.6 micron process to complete the design, emphasizing the modularization of functional units. The core of layout design is to reduce the area and optimize the performance. Because the logic adopts a relatively new design idea, there is no dynamic circuit and special unit, so the layout design mainly focuses on how to reduce the area with a compact design. Attention should be paid to the clock network. Because the CPU adopts four levels of clock, in order to ensure that each level of clock can work normally, a relatively large buffer is added at the driving end of the four clocks, and the width length ratio of the MOS tube of the buffer is adjusted appropriately to make the delay of its rising edge and falling edge not equal, so as to ensure that the four clocks do not overlap each other

rom design and ROM compiler research

stc001 chip ROM internal capacity of 2KB, word length of 12 bits. Due to the requirements of mass customization products, Rom adopts mask structure

in order to meet the needs of product function upgrading, it is necessary to change the ROM code point to complete the product upgrading. It takes a long time to fill the code points manually, and the reliability cannot meet the requirements. Therefore, a software is developed to automatically complete the whole process from program to layout. Different from the commonly used ROM compiler, this software is customized for ROM with a capacity of 2KB and a word length of 12 bits. The framework of ROM is completely customized and designed by hand, which can be reused, and the remaining code points are filled automatically by the program. In this way, the ROM generated under the premise of ensuring efficiency has high compactness

the main problem encountered is the overall simulation of the system. Although the MCU is not large, it is also a small system on chip (SOC), which integrates CPU, ROM, ram and analog circuits (such as electric reset and RC oscillator). The method of separate simulation is adopted here. First, the analog circuit is simulated with artist simulation tool, and then the simulation results are manually sent to Verilog XL for digital global simulation. Finally, LPE table is extracted from the layout, and the global post simulation is carried out with star SIM simulation software

the main performance indicators of stc001 control chip are: the first intermediate frequency is 479.5mhz, the image tuning range is 950m~2050m, the step size is 1MHz, the sound tuning range is 5m~10m, the step size is 10kHz, and the sound intermediate frequency is 10.7MHz; It has 4-bit common positive nixie tube drive display, which can display channel number, frequency value, various working states, etc; It can store 120 channel values (with 24C08 E2PROM); Full static CMOS, working voltage 3v~5.5v, crystal oscillator 4MHz; In addition, stc001 at this time, the oil in the oil cylinder will be injected into the oil cylinder through the servo valve, and then the conduit will return to the oil tank through the gap of the cylinder gap. If there is not much oil in the oil tank, it will be maintained for 50 minutes. The oil also has the functions of reserving the antenna azimuth control output interface, perfect silence function, antenna selection function, factory channel parameter preset function, horizontal/vertical polarization mode selection and so on

application circuit

Figure 2: application circuit diagram of stc001 for satellite TV reception

Figure 2 is the application circuit of stc001 for satellite TV reception, in which pins 10 to 17 of stc001 are multiplexed by key scanning and LED display drive; Pin 18 is connected to the output signal of the infrared receiving head; Pins 20 to 24 output control signals such as image and sound to the outside of the module; Pins 22 and 23 are connected to mt24lc02. Mt24l has many good properties that cannot be compared with other inorganic fillers: wide sources, low price, low density, good insulation, little wear on processing equipment. C02 is E2PROM, which is in a readable and writable state, and is used to save some necessary temporary data; Pin 28 is connected to a low-voltage reset circuit composed of five devices. (end)

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