Ⅰ. ARM

ARM (Advanced   Machines) is a well-known enterprise in the microprocessor industry, designing a large number of high-performance, cheap and low-energy  processors, related technologies, and software.

ARM is also a single-chip microcomputer. The ARM  architecture is the first RISC microprocessor designed for low-budget markets. It is basically the industry standard of 32-bit single-chip microcomputers. It provides a series of the kernel, system expansion, microprocessor, and system chip solutions. Four functional modules can be configured and produced by manufacturers according to the requirements of different users.

Because all products adopt a universal software system, the same software can run in all products. At present, ARM  accounts for more than 90 shares in the handheld device market, which can effectively shorten the application development and testing time and reduce research and development costs.

Ⅱ. DSP

DSP (digital signal processor) is a unique microprocessor with its own complete instruction system. It is a device that processes a large amount of information with digital signals. A digital signal processor includes control units, computing units, various registers and a certain number of storage units in a small chip. It can also connect several memory on its periphery and communicate with a certain number of external devices. It has comprehensive software and hardware functions, which itself is a Microcomputer.

The DSP  adopts  design, that is, the data bus and the address bus are separated, so that programs and data are stored in two separate spaces, allowing for complete overlapping of instructions and execution instructions. That is to say, the next instruction can be extracted and decoded while executing the previous instruction, which greatly improves the speed of the microprocessor.

It also allows transmission between program space and data space, because it increases the flexibility of the device. The working principle is to receive analog signals, convert them into 0 or 1, modify, delete and strengthen the digital signals, and interpret digital data back into analog data or actual environment formats in other system chips. It is not only programmable but also runs at tens of millions of complex instruction programs per second in real-time, far exceeding the general microprocessor. It is an increasingly important computer chip in the digital electronic world.

Its strong data processing ability and high running speed are the two most praiseworthy features. Because of its strong computing power, fast speed, small size, and high degree of flexibility in software programming, it provides an effective way to engage in various complex applications.

Main features of DSP chip

1. One multiplication and one addition can be completed in an instruction cycle.

2. The program is separated from the data space and can access instructions and data at the same time.

3. It has fast RAM  in the chip, which can usually be accessed in both blocks through a separate data bus.

4. Hardware support with low or no overhead loops and jumps

5. Fast interrupt handling and hardware support

6. Multiple hardware address generators that operate in a single cycle

7. Multiple actions can be performed in parallel.

8. Support assembly line operations, so that finger extraction, decoding, and execution can overlap.

Of course, compared with the universal microprocessor, other general functions of the DSP  chip are relatively weak.

Ⅲ. FPGA

FPGA (Field Programmable Gate Array) is the product of further development on the basis of programmable devices such as  etc. It is the most(ASIC). A tall one.

FPGA adopts a new concept of Logic Cell Array, which includes configurable logic module(Configurable Logic Block) and output input module IOB (Input O) Utput Block) and Interconnect is three parts.

Users can reconfigure the logic modules and  modules within  to realize the user's logic. It also has the characteristics of static repeatable programming and dynamic system reconstruction, so that the functions of hardware can be modified by programming like software. As a semi-customized circuit in the field of special not only solves the shortcomings of customized circuits but also overcomes the shortcomings of the limited number of gate circuits of the original programmable device.

It is no exaggeration to say that FPGA can complete the functions of any digital device, from high-performance CPU to simple 74 circuits, which can be implemented with FPGA. FPGA is like a piece of white paper or a pile of building blocks. Engineers can freely design a digital system through traditional schematic input methods or hardware description languages. Through software simulation, we can verify the correctness of the design in advance.

After the  is completed, you can also use the online modification ability of FPGA to modify the design at any time without changing the hardware circuit. Using FPGA to develop digital circuits can greatly shorten the design time, reduce the area and improve the reliability of the system.

FPGA is set by programs stored in the RAM  on the chip to set its working state, so the on-chip RAM  needs to be programmed when working. Users can adopt different programming methods according to different configuration modes. When powered up, the FPGA chip reads the data from EPROM into the in-chip programming RAM,  After configuration is completed, the FPGA enters the working state. After the power is off, FPGA is restored to the white film, and the internal logical relationship disappears, so FPGA can be used repeatedly.

FPGA programming does not require a dedicated FPGA programmer, just a universal EPROM and PROM programmer. When you need to modify the FPGA function, just change an EPROM. In this way, the same FPGA and different programming data can produce different circuit functions. Therefore, the use of FPGA is very flexible. It can be said that the FPGA chip is one of the best choices for small batch systems to improve system integration and reliability.

Ⅳ.  So what are the differences between them?

ARM has strong transaction management functions, which can be used to run interfaces and applications. Its advantages are mainly reflected in control, while DSP  is mainly used for computing, such as encryption and decryption, modem and demodulation, etc. Its advantages are strong data processing ability and high running speed.

FPGA can be programmed with or Verilog HDL, which is flexible. Because it can program, debug, reprogram and repeat operations, it can fully develop and verify the design. When there are a small number of changes in the circuit, it can show the advantages of FPGA. Its field programming ability can extend the life of the product in the market, and this ability can be used to upgrade or debug the system.

As a Processor, what are the advantages and disadvantages of these devices? In fact, C51, ARM  and DSP  are not provided to users as chips alone, but need to be supported by some peripheral circuits. For example: memory controller, interrupt controller, timer,  etc.

Compare from the perspective of processor

C51 is 8-bit, ARM is 32-bit, DSP is 16-bit, and there are also higher.

In terms of computing power, C51 is the weakest, DSP  is the strongest, and ARM  is centered.

The structure varies greatly. The simplest C51 is the general Vonne Norman structure, the RISC above ARM  9 is the  structure, and the DSP  generally uses the Harvard structure.

Generally, the chip area of C51 is very small, and the working frequency is very low (usually more than 10 MHz, some are 24MHz), so the power consumption is low;  is very high (the height reaches more than 300MHz), so the power consumption is large; the area of the ARM  chip is also very small, and the ARM  7 is 0.55 square millimeters. The power consumption is also relatively small. The frequency is about (between dozens and 200MHz)

Therefore, C51 is mainly used in control systems that do not require too much computing, generally equipped with rich peripheral modules;  is mainly used in high-end systems that require complex computing, such as image processing, encryption, and decryption, navigation systems, etc., and peripheral modules are generally less; It's a compromise between C51 and DSP, 

Emphasize one point: C51's performance is far inferior to that of  and DSP.  but it still occupies an important place because of the performance-price ratio; because it is too mature, too small, too cheap, and DSP is also indispensable in some areas that require complex computing; ARM's success is that he has found a compromise. Heartfelt points and establish a very flexible business model

Ⅴ. CPLD

CPLD (Complex Programmable Logic Device) is a complex programmable logic device developed from devices. It is relatively large in scale and complex in structure and falls within the scope of large-scale integrated circuits.

It is athat which users construct logical functions according to their own needs. The basic design method is to generate the corresponding target file with the help of the integrated development software platform, use a schematic diagram, hardware description language and other methods, and transfer the code to the target chip by downloading the cable ("programming in the system") to realize the designed digital system.

Ⅵ.  The difference between FPGA and CPLD 

The identification and classification of FPGA and CPLD are mainly based on their structural characteristics and working principles. The usual classification method is to call devices that form logical behaviors by-product item structure CPLD.  such as Lattice's ispLSI series,XC9500 series, s MAX7000S series, and Lattice (former Vanti) S) Mach series, etc. Devices that form logical behaviors by table lookup are called FPGA, such as Xilinx's SPARTAN series, Altera's FLEX10K or ACEX1K series.

Although FPGA and CPLD  are both programmable ASIC  devices and have many common characteristics, they have their own characteristics due to differences in CPLD  and FPGA structures.

Respective characteristics

CPLD is more suitable for completing various algorithms and combination logic, and FPGA is more suitable for completing timing logic. In other words, FPGA is more suitable for structures rich in triggers, while CPLD  is more suitable for structures with limited triggers and rich product items.

The continuous wiring structure of CPLD  determines that its timing delay is uniform and predictable, while the segmented wiring structure of FPGA determines the unpredictability of its delay.

FPGA is more flexible than CPLD  in programming. CPLD  is programmed by modifying the logical function with fixed internal connection circuits. FPGA is mainly programmed by changing the wiring of the internal connection; FPGA can be programmed under the logic gate, while is programmed under the logic block.

FPGA is more integrated than CPLD.  with a more complex wiring structure and logical implementation.

CPLD is more convenient to use than FPGA. programming adopts  or FASTFLASH technology, which is simple to use without external memory chips, while FPGA programming information needs to be stored on external memory, and the usage method is complicated.

CPLD is faster than FPGA and has greater time predictability. This is because FPGA is gate-level programming, and the adopts distributed interconnection, while is logical block-level programming, and the interconnection between logical blocks is set-general.

In terms of programming methods, CPLD is mainly based onprogramming, with up to 10,000 times. The advantage is that programming information is not lost when the system is powered off. CPLD can be divided into two categories: programming or the programmer and system programming; FPGA is mostly based on SRAM programming. The program, programming information is lost when the system is powered off. Every time it is powered on, the programming data needs to be rewritten into SRAM from the outside of the device. Its advantage is that it can be programmed any time and quickly programmed at work, so as to realize dynamic configuration at the board and system levels.

CPLD is confidential and FPGA is poor.

Generally speaking, CPLD consumes more power than FPGA, and the higher the integration, the more obvious it is.