MSP430 MCUclock system
The MSP430 can optionally use up to three oscillators depending on the model. We can choose the appropriate frequency of oscillation according to the need, and can turn off the oscillator at any time when not needed to save power. The three oscillators are:
(1)DCO NC RC oscillator. It's inside the chip and can be turned off when not in use. The oscillation frequency of the DCO is affected by the ambient temperature and the working voltage of the MSP430, and the frequency generated by the same type of chip is different. But the adjustment function of DCO can improve its performance. Its adjustment is divided into the following three steps: a: select BCSCTL1.RSELx to determine the nominal frequency of the clock; b: Select DCOCTL.DCOx in the nominal frequency base segment coarse tuning; c: Select the value of DCOCTL.MODx for fine-tuning.
(2)LFXT1 is connected with low frequency oscillator. Typically, it is connected to a 32768HZ clock oscillator, at which time the oscillator does not need to be connected to a load capacitor. Can also be connected to 450KHZ~8MHZ standard crystal oscillator, at this time need to connect the load capacitor.
(3)XT2 is connected to a standard crystal oscillator of 450KHZ~8MHZ. In this case, you need to connect the load capacitor, which can be turned off when not in use.
Low frequency oscillators are used to reduce energy consumption, such as in battery-powered systems, and high frequency oscillators are used to respond to events or to perform heavy calculations by the CPU.
MSP430 three clock signals: MCLK system master clock; SMCLK system sub-clock; ACLK clock.
(1)MCLK system master clock. In addition to CPU operations using this clock, modules can also be used. MCLK can select the clock signal generated by any oscillator and perform 1, 2, 4, 8 frequency division as its signal source.
(2)SMCLK system sub-clock. For use by modules. Before use, frequency division can be realized through the register of each module. SMCLK can select the clock signal generated by any oscillator and perform 1, 2, 4, 8 frequency division as its signal source.
(3)ACLK clock. For use by modules. Before use, frequency division can be realized through the register of each module. However, ACLK can only be divided into 1, 2, 4 and 8 frequencies by LFXT1 as signal source.
After the PUC is reset, the signal source of MCLK and SMCLK is the DCO, and the oscillation frequency of DCO is 800KHZ. The signal source of ACLK is LFXT1.
The MSP430 contains an internal crystal oscillator failure monitoring circuit that monitors the clock signals of the LFXT1(operating in HF mode) and XT2 outputs. When the clock signal was lost by 50us, the monitoring circuit picked up the oscillator failure. If the MCLK signal comes from LFXT1 or XT2, MSP430 automatically switches the MCLK signal to DCO so that the program can continue running. But the MSP430 does not monitor the LFXT1 operating in low frequency mode.
Before talking about the development process of domestic EDA, we should first understand the history of EDA industry. In the 1980s, the rapid development of the chip pushed the commercial computer into the high speed, and thus promoted the rise of the CAD industry. EDA is a typical representative.
In the early stage of the IC industry, chip design was achieved by manual wiring. But with the increase of chip integration, the shortage of manual wiring became more and more difficult, which coincided with the rise of the computer, and EDA came into being, which led to the birth of Calma, ComputerVision, Applicon, Mentor Graphics, Daisy and Valid companies. With the help of this electronic automatic tool, they can operate the front and back end technology of the chip design and the verification technology on the computer to help the chip best wiring, verification and simulation.
After years of mergers and acquisitions, only Cadence, Synopsys and Mentor remain in the field of integrated circuit EDA. The influence of markets is also increasingly concentrated. But in fact, since the middle and late 1980s, China has been invested in the research and development of EDA industry.
Data shows that at that time, domestic high-tech fields including integrated circuits were trapped in the "Batumi" embargo, the development was hampered. In order to develop the integrated circuit industry, China mobilized 17 units and more than 200 gathered in the former integrated circuit Design Center in 1986 to develop China's free integrated circuit computer design system -- Panda system.
After many years of difficulties, the first EDA panda system was finally launched in 1993, and the subsequent development can be described as a step by step in 10 years. In 2001, the domestic IC design unit launched the Zeni system of Jiutian, which attacked the overseas market while serving the local demand. In 2009, * set up a new company, Huada Jiutian, to promote the development of domestic EDA. This will be later.
Although due to subjective and objective reasons, the domestic EDA industry did not succeed in the secular sense, but in this process, there have been a number of EDA manufacturers sprout in China. According to the relevant data, in 2008, the domestic EDA research companies also have China Electronics, Huatian Zhonghui, core vision, Exeli, Shengjing micro, technology industry thinking, Guangli micro and the United States and other several. After another ten years of development, Huada Jiutian, Xinhe Technology, Guangliwei,
Bodawei and other enterprises broke out from the domestic EDA formation:
Bearing the technology of Panda system, Huada Jiutian has accumulated many years in EDA and IP. Now they can provide digital-analog hybrid/fully customized IC design, FPD whole process design and SoC digital back-end optimization direction of EDA solutions. Especially in the field of FPD, Huada Jiutian * has become the best supplier of FPD design solutions for the whole process, and has gained the market share of most panel factories.