FPGA is a programmable silicon chip, DSP is digital signal processing, when system designers face the important issue of using FPGA or DSP in the architectural design stage of the project. This article will first introduce the characteristics of FPGA and DSP, and then analyze the difference between the two from the perspective of internal resources, programming language, and functionality.
1, the characteristics of FPGA and DSP
FPAG structural features
There are a large number of logic gates and flip-flops on the chip, mostly for the lookup table structure, and the implementation process is mostly SRAM. Large scale, high integration, fast processing speed and high execution efficiency. Can complete complex sequential logic design, and programming is flexible, convenient, simple, and can be repeated multiple times. Many FPAGs can be programmed indefinitely. Reconfiguration can reduce hardware overhead. The disadvantage is that the original logic configuration will be lost after power failure; the timing is difficult to plan; multiple events cannot be processed; it is not suitable for conditional operations.
DSP structural characteristics
1. Harvard structure and improved Harvard structure separated by data and program, the execution instruction is faster.
2. Adopt pipeline technology to reduce the execution time of each instruction.
3, on-chip multi-bus, can take instruction and multiple data access operations at the same time.
4. Independent accumulator and adder can perform multiplication and accumulate operations simultaneously in one cycle.
5, there are DMA channel controller and serial communication port, etc., to facilitate data transmission.
6. There are interrupt processors and timing controllers to facilitate the formation of small-scale systems.
7, with hardware and software waiting function, can interface with a variety of memory.
As a special microprocessor, DSP is mainly used for calculation. The advantage is the flexibility of software. Suitable for conditional processes, especially complex multi-algorithm tasks. The DSP is programmed in assembly or in a high-level language (such as C language) to implement the solution in real time. Therefore, the advantage of using DSP devices is that the software update speed is fast, which greatly improves the reliability, versatility, interchangeability and flexibility of the system. Disadvantages: limited by serial instruction stream; more than a few MHZ sampling rate, a DSP can only complete very simple operations on data; long development cycle.
2, internal resources
The FPGA focuses on designing a hardware circuit with a certain function. The internal resource is a tiny unit such as VersaTIles (ActelFPGA). The internal unit of the FPGA is originally designed to describe the hardware circuit in HDL language before programming. The wiring resources inside the FPGA connect the signals between the internal and the modules of these functional modules to form a larger module. FPGA can implement ALU, adder, multiplier, accumulator, FIFO, SRAM, DDRcontroller, FFT, HDLC, DMA, PWM and other digital circuits internally, which means we use it to implement a specific or general hardware function. One or more modules, each of which requires HDL to describe the design implementation.
The current FPGAs can directly embed microprocessors such as ARM7, CoretexM1, Core8051, etc., for the soft core of the FPGA, and some FPGA manufacturers directly implement some hardware modules into the FPGA. These are hard cores inside the FPGA. Traditional FPGAs are all implementing pure digital circuits. Only Actel's FPGAs implement digital-to-analog hybrid PSC single-chip technology, which truly enhances and expands the application functions and fields of FPGAs.
In addition, most FPGAs have PLL, DLL and other phase-locked loops, Slew adjustable, Actel also built-in hardware units such as OSC, RTC, Powermanager, and even Actel's Fusion series also built a 600kbps 12bit ADC and MOSFET Driver and other analog interfaces, internal UserFlashMemeory, FlashROM and other resources can achieve real PSC, Bootloader and other functions.
DSP is mainly algorithm processing, internal resources are mainly multipliers, adders and other resources, SPI interface, UART interface, accept a certain instruction set, the internal resources are basically ready-made, need to be reconfigured by the needs of customers It is convenient for customers to use, but its function is relatively limited, so it is mainly used in certain specific fields. DSP also has embedded phase-locked loops, counters, Baudrate generators, and some DSPs also have ADC analog interfaces.
3, programming language
FPGAs mainly use HDL, including VHD1, Verilog, and the digital-analog mixed description language Verilog-AMS. (Course recommendation: FPGA training)
DSP uses C, assembly language programming. (Course recommendation: C6000 DSP training)
4, functional angle
FPGAs are commonly used to implement digital circuit blocks, and basically implement all digital circuits, traditional digital function modules, and digital processing modules for customer-specific requirements. FPGAs have a wide variety of IO bridges, and different types of FPGAs support different IO standards and protocols, but the drive capability or voltage of these IOs are programmable. The implementation of any digital function circuit, the processing of high-speed signals, the signal processing in the control field, the implementation of the bridge conversion protocol, Actel's Fusion can also be used for current/voltage detection, temperature detection, MOSFETdriver, power management, and its unique Flash process. Technology can rely on battery power, and power-down data storage in real time, ultra-low power consumption, multiple working modes (StaTIc, Sleepmode), especially the function of IGLOO chip consumes only 5uW in Sleepmode. Such power consumption can be used for mobile phones, mobile handheld devices such as GPS to play a larger functional application.
In addition, the FPGA is used to implement the pre-design verification of the ASIC, the FPGA implements the functions of the DSP, realizes the functions of the CPU, the functions of the MCU, the memory controller, and the forward and reverse transformation of the industrial PWM, SVPWM, Clarke, Park. Implementation, VGA control, data encoding and decoding, demultiplexing, processing of signals up to Gbps, protocol conversion implementation, etc., are all difficult for DSP.
There are many off-the-shelf hardware modules and interfaces and controllers inside the DSP, but software programming is required to implement PWM control, interface control, UART interface, SPI interface and other functions. However, due to the limitation of the clock cycle of the instruction set, the DSP cannot handle too high a signal. As for the Gbps signal, signals such as LVDS are difficult to be involved. Therefore, the corresponding application areas will be limited. However, customers in different fields have different design schemes, and the focus is different. Some domain designers also like to use DSP, such as algorithm implementation, protocol processing, etc. If you switch to FPGA to deal with it, it will not be worth the candle.
5. Applicable occasions
DSP is suitable for system low sampling rate, low data rate, multi-condition operation, processing complex multi-algorithm tasks, programming in C language, and floating point using system. Suitable for multi-conditional processes, especially complex multi-algorithm tasks, at lower sampling rates.
FPAG is suitable for high-speed sampling rate (≥ MHZ), high data rate, block mode programming, fixed or repeated processing tasks, and fixed point. It is suitable for high-speed sampling frequency, especially when the task is relatively fixed or repeated, as well as the prototype and system development.
Displacement sensor, also known as linear sensor, is a linear device belonging to metal induction. The function of the sensor is to convert various measured physical quantities into electricity. In the production process, the measurement of displacement is generally divided into measuring the physical size and mechanical displacement. According to the different forms of the measured variable, the displacement sensor can be divided into two types: analog and digital. The analog type can be divided into two types: physical property type and structural type. Commonly used displacement sensors are mostly analog structures, including potentiometer-type displacement sensors, inductive displacement sensors, self-aligning machines, capacitive displacement sensors, eddy current displacement sensors, Hall-type displacement sensors, etc. An important advantage of the digital displacement sensor is that it is convenient to send the signal directly into the computer system. This kind of sensor is developing rapidly, and its application is increasingly widespread.
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