What are the different ways of describing structures?
There are 3 different descriptions:
The behavior description method, the data flow description method, and the structure description method describe the function of the structure from different aspects.
What are the characteristics of Byteflight?
- The bit transmission rate is 10Mb/s, and the net data transmission rate is 5Mb/s.
- The maximum data refresh time is 250/s.
- Adopt the coding mode of NRZ with start bit and stop bit.
- The protocol itself does not define a limit on the number of nodes.
- The protocol does not define the network topology.
- There is no need to specify the address of the receiving end when the information is transmitted, and the information itself identifies the receiving node.
- Synthesize the advantages of synchronous bus and asynchronous bus.
- The access to the bus is completely event-triggered and controlled by the protocol control hardware.
- Even when the bus is at the maximum load, the timely transmission of a certain amount of the highest priority information can be guaranteed, that is, the bus will not be “blocked” for the highest priority information.
- When the bus load is low, the low-priority information can access the bus in an asynchronous manner.
- An alarm state can be sent over the same physical medium, and this state can be detected by two independent components.
What are the advantages and disadvantages of a synthetic carbon film potentiometer?
The advantages are high stability, high resolution, the same wide resistance range, long life and small size.
The disadvantages are large current noise, poor nonlinearity, moisture resistance, low power and poor resistance stability.
What is the goal of system power management?
The goal of system power management is to minimize the total power consumption of electronic devices.
What are the characteristics of metal film Resistorss?
Metal film resistors have good heat resistance and temperature resistance, and can work normally and stably up to 70 degrees Celsius.
Because the film layer is metal, metal film resistors have higher resistance to current impact than carbon film resistors, and the load capacity is also stronger.
Therefore, the volume to power ratio of metal film resistors is smaller than that of carbon film resistors. Metal film resistors have higher power than carbon film resistors when the resistor volume is the same.
Not only that, metal film resistors also have the characteristics of small resistance error, small noise coefficient, good voltage stability, good high-frequency characteristics, and strong hardness of the metal film layer attached to the base.
How to connect without using dual network card?
Connect the ADSL Modem to the hub (a network card is saved, and one more hub port is occupied), and each host is also connected to the hub. Each host can establish a broadband connection. Of course, only one host can establish a broadband connection at the same time, which can be shared by other hosts.
This eliminates the need for a specific host to always be powered on to serve other hosts, but other hosts need to figure out a way to know the IP address of the host with the broadband connection and set it as a proxy server or gateway. It’s not a big problem at home or in the office, just ask.
The specific configuration is as follows:
(1) Establish a broadband connection on a host, and dial up the Internet to connect it to the Internet.
(2) If it is a dual network card mode, it needs to be set in the network card properties of the LAN port of the host. In the network property settings of its LAN port, configure it to a different subnet from the WAN port (generally after the ADSL connection is established, the IP address of the WAN port is 192.168.0.1, and the subnet mask is 255.255. 255.0), such as 192.168. X. 1 (X is not 0) and used as the gateway address of other hosts. If the dual network card mode is not used, 192.168.0.1 is used as the gateway address of other hosts.
(3) In the network attribute settings of other hosts sharing the ADSL Internet access, configure it to the network with the LAN port network card as the gateway (IP address is set to 192.168.X.Y, the last field Y is optional The range is 2 to 254).
What are the sources of internal noise from FETs?
- Channel thermal noise
- Gate shot noise
- 1/f noise
- Gate induced noise
What are the basic elements of a cryptosystem?
Cryptographic algorithms and keys.
What is the photoelectric effect？
Light shines on certain substances, causing changes in the electrical properties of the substances. This kind of photoelectric change phenomenon is collectively referred to as the photoelectric effect of the metal surface emitting electrons under the action of light irradiation. The emitted electrons are called photoelectrons.
When the wavelength of light is less than a certain critical value, electrons can be emitted, that is, the limit wavelength, and the corresponding frequency of light is called the limit frequency. The critical value depends on the metal material, and the energy of the emitted electrons depends on the wavelength of the light but not on the intensity of the light, which cannot be explained by the wave nature of light.
Another point that contradicts the wave nature of light is the instantaneous nature of the photoelectric effect. According to the wave theory, if the incident light is weak, the irradiation time will be longer. The electrons in the metal can accumulate enough energy to fly out of the metal surface.
But the fact is, as long as the frequency of light is higher than the limit frequency of metal. Regardless of the brightness of the light, photons are produced almost instantaneously, no more than ten seconds to the minus ninth power.
The correct explanation is that light must be composed of strictly defined energy units (ie photons or photons) related to wavelength. This explanation was proposed by Einstein.
The photoelectric effect was discovered by German physicist Hertz in 1887 and played a fundamental role in the development of quantum theory. Under the irradiation of light, the phenomenon that the electrons in the object are extracted is called the photoelectric effect.
Photoelectric effect is divided into photoelectron emission, photoconductive effect and photovoltaic effect. The former phenomenon occurs on the surface of the object, also known as the external photoelectric effect. The latter two phenomena occur inside objects and are called the internal photoelectric effect.
In the photoelectric effect, the direction of electron emission is not completely directional. It’s just that most of them are emitted perpendicular to the metal surface, regardless of the direction of the light, light is an electromagnetic wave. However, light is an orthogonal electromagnetic field oscillating at high frequency, and its amplitude is very small, so it will not affect the direction of electron emission.
What is NiosII?
The NiosⅡseries embedded processor is the second-generation soft-core embedded processor solution introduced by Altera.
The Nios II processor core is a 32-bit general-purpose RISC processor using pipeline technology and Harvard architecture. It features a shared common instruction set structure optimized for Altera’s mainstream FPGA families.
The NiosⅡ processor series can be widely used in fields that require general-purpose 32-bit embedded microprocessors. In contrast to hard-core processors, processors are implemented through intellectual property (IP) written in a hardware description language (HDL). Developers get the most suitable solution because they can choose the combination of peripherals, performance and processor that best suits their system needs.
The essence of hard core implementation is ASIC (Application Specific Integrated Circuits (ICs)), which does not have such high flexibility. And it takes a long time to complete the configuration, so that the latest process technology cannot be fully utilized. On the other hand, the soft-core processor can be transplanted into the latest FPGA technology immediately, such as StratixⅡ or CycloneⅡ series devices based on 90nm process.
NiosⅡseries embedded processor is a general-purpose RISC structure CPU, which is positioned in a wide range of embedded applications. The NiosⅡ embedded processor is the second-generation configurable soft-core processor for programmable logic devices launched by Altera in June 2004, with a performance exceeding 200DMIPS.
Nios II is a RISC general-purpose embedded processor soft core based on Harvard architecture, which can be combined with user logic and programmed into Altera’s FPGA. The processor has a 32-bit instruction set, 32-bit data paths and configurable instruction and data buffering. It is especially optimized for programmable logic and a comprehensive solution for programmable system-on-a-chip.
The Nios II processor family includes three cores:
One is the high-performance kernel (Nios II/f);
The second is the low-cost kernel (NiosⅡ/e);
The third is the standard kernel (Nios II/s) with a compromise between performance and cost, which is the balance of the first two.
Each is optimized for a different performance range and cost. All three cores use a common 32-bit instruction set (ISA), which is binary compatible. Using industry-leading design software, Altera’s Quartus II software and SOPC Builder tools, engineers can easily embed Nios II processors into their systems.
The NiosⅡ processor system consists of NiosⅡCPU and a series of peripherals. The interfaces of NiosⅡCPU, on-chip peripherals, on-chip memory and peripherals are all implemented on Altera’s chips, which are equivalent to implementing a computer or microcontroller on a single chip.
Since FPGA is programmable, NiosⅡ processor can be implemented on FPGA to tailor its characteristics according to the designer’s needs to make it meet the requirements of performance and cost.
Therefore, Nios II is a configurable soft-core processor. “Configurable” means that the designer can add or subtract processor functionality based on performance and cost requirements. “Soft core” means that the Nios II processor is not implemented by a fixed hard chip like ARM, but is implemented by software design, and then the FPGA chip is configured with design files.
That is to say, Altera does not sell NiosⅡ processor chips, but sells blank FPGAs and provides corresponding IP cores for NiosⅡ systems. Users can form Nios II system by these IP cores according to application needs, and then download this system to FPGA to realize.
COMMENTS