Programmable Logic Devices (PLDs) have revolutionized the design of digital systems. His influence is no less than the invention and use of the MCU in the 1970s. It is no exaggeration to say that the PLD can perform any digital device function, up to the high-performance CPU, down to the simple 74 circuit. Using PLDs to develop digital circuits can significantly reduce design time, reduce PCB area, and increase system reliability. These advantages of PLD have enabled PLD technology to develop rapidly after the 1990s, becoming the most dynamic and promising technology in the field of electronic design.
At present, this technology PLD extends two branches according to its internal structure, namely Complex Programmable Logic Device (CPLD) and Field Program-MableGate Array (FPGA), which are collectively referred to as programmable logic. Device or CPLD/FPGA.
1 PLD development process
Early programmable logic devices were only programmable read only memory (PROM), ultraviolet erasable read only memory (EPROM), and electrically erasable read only memory (E2PROM). Due to structural limitations, they can only perform simple digital logic functions.
Later on, there was a class of slightly more complex programmable chips, the programmable logic device (PLD), which was able to perform a variety of digital logic functions. At this stage (around the mid-1970s), the main products were Programmable Array Logic (PAL). The PAL consisted of a programmable AND plane and a fixed OR plane. The output of the OR gate can be The trigger is selectively set to the registered state. The PAL device is field programmable, and its implementation process includes anti-fuse technology, EPROM technology and E2PROM technology.
In the early 1980s, on the basis of PAL, a general array logic (Generic Array Logic, GAL) was developed. He used the E2PROM process to realize the electrical rewritable and electrically rewritable. The output structure is programmable logic. The macro unit, and thus his design is very flexible, and many people still use it.
In the mid-1980s, in order to make up for the above defects, Erasable Programmable Logic Devices (EPLD) were introduced. CPLD and FPGA, EPLD have higher integration and more flexible design, but the internal connection function is weaker.
2 Structure comparison
Different manufacturers call PLD differently, but in general, the PLD based on the product item technology, FLASH (similar to E2PROM process) is called CPLD; based on the look-up table technology, SRAM process, PLD called E2PROM is called FPGA. The following compares the two from the internal structure.
What is Car Ethernet
Car Ethernet is a new local area network technology that uses Ethernet to connect the electronic unit in the car. Unlike traditional Ethernet, which uses 4 unshielded twisted pair cables, car Ethernet can achieve a transmission rate of 100Mbit/s or even 1Gbit/s on a single pair of unshielded twisted pair cables. At the same time, it also meets the requirements of the automotive industry for high reliability, low electromagnetic radiation, low power consumption, bandwidth allocation, low latency and synchronous real-time. The physical layer of on-board Ethernet uses BroadRReach technology, and BroadR-Reach's physical layer (PHY) technology has been standardized by the One-pair Ethernet Alliance (OPEN). Therefore, it is sometimes called Broad RReach (BRR) or OABR (Open Alliance BroadR-Reach). The MAC layer of vehicle Ethernet adopts the IEEE 802.3 interface standard and seamlessly supports widely used high-level network protocols (such as TCP/IP) without any adaptation.
On-board Ethernet protocol architecture
Vehicle-borne Ethernet and its supported upper-layer protocol architecture are shown in Figure 1. Vehicle-borne Ethernet mainly involves OSI layer 1 and Layer 2 technologies, while vehicle-borne Ethernet also supports AVB, TCP/IP, DOIP, SOME/IP and other protocols or application forms.
On-board Ethernet framework
Among them, AVB is an extension of traditional Ethernet functions, which enhances the real-time performance of traditional Ethernet audio and video transmission by adding precise clock synchronization, bandwidth reservation and other protocols, and is a network audio and video real-time transmission technology with great development potential. SOME/IP (Scalable Service-Oriented MiddlewarE on IP) specifies the video communication interface requirements for vehicle camera applications, which can be applied to the field of vehicle cameras, and realizes the mode control of driver assistance cameras through apis.
As an extension of AVB protocol, Time-Sensitive Networking (TSN) introduces related technologies of time-triggered Ethernet, which can efficiently realize the transmission of automotive control information. In addition, the on-board Ethernet of the 1Gbit communication standard also supports Power Over Ethernet (POE) function and Energy-Efficient Ethernet (EEE) function. The POE function provides power for connected terminal devices while transmitting data through twisted pair cables, eliminating the need to connect external power cables to terminals and reducing the complexity of power supply.
On-board Ethernet standardization
In terms of in-vehicle Ethernet standardization, the IEEE802.3 and IEEE802.1 working groups, AUTOSAR, the OPEN Alliance and the AVnu Alliance have played a major role in promoting it.
The IEEE802.3 local area network standard represents the mainstream Ethernet standard in the industry, and the on-board Ethernet technology is developed on the basis of IEEE802.3, so the IEEE is currently the most important international standardization body for on-board Ethernet. In order to meet the requirements of the car, it involves the development of a number of new specifications and the revision of the original specifications within the two working groups of IEEE802 and 802.1, including PHY specifications, AVB specifications, and single-wire to data line power supply. In addition, AVB related to AV transmission, timing synchronization and other specifications also need to be standardized by other technical committees of IEEE, such as IEEE1722 and IEEE1588.
OPEN Alliance
The OPEN Industry Alliance was launched in November 2011 by Broadcom, NXP, and BMW to promote the application of Ethernet-based technology standards to in-car connectivity. The main standardization goal is to develop a 100Mbit/s BroadR-R physical layer standard and develop OPEN interoperability requirements.
AUTOSAR
AUTOSAR is a consortium of automotive manufacturers, suppliers, and tool developers that aims to develop an open, standardized automotive software architecture, and the AUTOSAR specification already includes the automotive TCP/UDP/IP protocol stack.
AVnu
The AVnu Alliance was formed by Broadcom in collaboration with Cisco, Harman and Intel to promote the IEEE 802.1 AVB standard and the Time Synchronization Network (TSN) standard, establish a certification system, and address important technical and performance issues such as precise timing, real-time synchronization, bandwidth reservation, and traffic shaping.
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