History of CAN technology
In February of 1986, Robert Bosch GmbH introduced the Controller Area Network (CAN) serial bus system at the Society of Automotive Engineers (SAE) congress. It was the hour of birth for one of the most successful network protocols ever. Today, almost every new passenger car manufactured in Europe is equipped with at least one CAN network. Used also in other types of vehicles, from trains to ships, as well as in industrial controls, CAN is one of the most dominating bus protocols – maybe even the leading serial bus system worldwide.
1986年2月，Robert Bosch GmbH 在汽车工程师协会（SAE）大会上推出了控制器局域网（CAN）串行总线系统。 这是有史以来最成功的网络协议之一的诞生时刻。 如今，几乎所有在欧洲制造的新乘用车都配备了至少一个CAN网络。 CAN也可用于其他类型的车辆，从火车到船舶，以及工业控制，是最主要的总线协议之一 - 甚至可能是全球领先的串行总线系统。
From the idea to the first chip 从想法到第一款芯片
In the early 1980s, engineers at Bosch were evaluating existing serial bus systems regarding their possible use in passenger cars. Because none of the available network protocols were able to fulfill the requirements of the automotive engineers, Uwe Kiencke started the development of a new serial bus system in 1983.
上世纪80年代初，Bosch 的工程师们对现有的串行总线系统进行了评估，以确定它们在汽车上的可能的用途。由于现有的网络协议都不能满足汽车工程师的要求，Uwe Kiencke 于1983年开始开发新的串行总线系统。
The new bus protocol was mainly supposed to add new functionalites – the reduction of wiring harnesses was just a by-product, but not the driving force behind the development of CAN. Engineers from Mercedes-Benz got involved early on in the specification phase of the new serial bus system, and so did Intel as the potential main semiconductor vendor. Professor Dr. Wolfhard Lawrenz from the University of Applied Science in Braunschweig-Wolfenbüttel, Germany, who had been hired as a consultant, gave the new network protocol the name ‘Controller Area Network’. Professor Dr. Horst Wettstein from the University of Karlsruhe also provided academic assistance.
新的总线协议主要是为了增加新的功能——减少线束只是副产品，而不是 CAN 开发背后的驱动力。梅赛德斯-奔驰(Mercedes-Benz)的工程师很早就参与了新串行总线系统的规格设计阶段，英特尔(Intel)作为潜在的主要半导体供应商也是如此。德国 Braunschweig-Wolfenbüttel 的 Applied Science 大学的Wolfhard Lawrenz 教授被聘为顾问，他将这种新的网络协议命名为“Controller Area Network（控制器区域网络）”。Karlsruhe大学的 Horst Wettstein 教授也提供了学术上的帮助。
In February of 1986, CAN was born: at the SAE congress in Detroit, the new bus system was introduced as the ‘Automotive Serial Controller Area Network’. Uwe Kiencke, Siegfried Dais, and Martin Litschel introduced the multi-master network protocol. It was based on a non-destructive arbitration mechanism, which grants bus access to the message with the highest priority without any delays. There was no central bus master. Furthermore, the fathers of CAN – the individuals mentioned above plus Bosch employees Wolfgang Borst, Wolfgang Botzenhard, Otto Karl, Helmut Schelling, and Jan Unruh – had implemented several error detection mechanisms. The error handling also included the automatic disconnection of faulty bus nodes in order to keep up the communication between the remaining nodes. The transmitted messages were not identified by the node address of the transmitter or the receiver of the message (as in almost all other bus systems), but rather by their content. The identifier representing the content of the message also had the function of specifying the priority of the message within the system.
1986年2月，CAN 诞生：在底特律的 SAE 大会上，新的总线系统被引入作为“汽车串行控制器区域网络”。 Uwe Kiencke，Siegfried Dais 和 Martin Litschel介绍了这个多主网络协议。 它基于一种非破坏性的仲裁机制，该机制允许总线访问具有最高优先级的消息而没有任何延迟。 并且，不需要在总线上设置主控制器。 此外，CAN 之父 - 上面提到的几个教授个人以及 Bosch 员工 Wolfgang Borst，Wolfgang Botzenhard，Otto Karl，Helmut Schelling 和 Jan Unruh —— 已经实现了数种在CAN中的错误检测机制。 该错误检测也包括自动断开故障节点功能，以确保能继续进行剩余节点之间的通讯。传输的报文并非根据报文发送器/接收器的节点地址识别（几乎其它的总线都是如此），而是根据报文的内容识别。同时，用于识别报文的标识符也规定了该报文在系统中的优先级。
A lot of presentations and publications describing this innovative communication protocol followed, until in mid 1987 – two months ahead of schedule – Intel delivered the first CAN controller chip, the 82526. It was the very first hardware implementation of the CAN protocol. In only four years, an idea had become reality. Shortly thereafter, Philips Semiconductors introduced the 82C200. These two earliest ancestors of CAN controllers were quite different concerning acceptance filtering and message handling. On one hand, the FullCAN concept favored by Intel required less CPU load from the connected micro-controller than the BasicCAN implementation chosen by Philips. On the other hand, the FullCAN device was limited regarding the number of messages that could be received. The BasicCAN controller also required less silicon. In today’s CAN controllers, a mixture of both concepts of acceptance filtering and message handling are implemented. This made the misleading terms BasicCAN and FullCAN obsolete.
之后，许多文章和出版物描述了这种创新的通信协议，直到1987年中期 - 提前两个月 - 英特尔交付了第一个 CAN 控制器芯片 82526。这是 CAN 协议的第一个硬件实现。 仅仅四年时间，一个想法就变成了现实。 此后不久，飞利浦半导体推出了 82C200。 这两个最早的 CAN 控制器祖先在接收过滤和消息处理方面有很大不同。 一方面，与飞利浦选择的 BasicCAN 实现相比，英特尔所青睐的FullCAN 概念所需的连接微控制器的 CPU 负载更少。 另一方面，FullCAN 设备在可以接收的消息数量方面受到限制。 BasicCAN 控制器仅需较少的硅晶体。 在今天的 CAN 控制器中，实现了接受过滤和消息处理两种概念的混合。 这使得BasicCAN 和 FullCAN 的误导性术语已经过时。
Standardization and conformity 标准化和一致性
The Bosch CAN specification (version 2.0) was submitted for international standardization in the early 1990s. After several political disputes, especially involving the ‘Vehicle Area Network’ (VAN) developed by some major French car manufacturers, the ISO 11898 standard was published in November 1993. In addition to the CAN protocol, it also standardized a physical layer for bit-rates up to 1 Mbit/s. In parallel, a low-power, fault-tolerant way of data transmission via CAN was standardized in ISO 11519-2. This was never implemented due to weaknesses in the standard. In 1995, the ISO 11898 standard was extended by an addendum describing the extended frame format using 29-bit CAN identifier.
Bosch CAN规范（2.0版）于20世纪90年代初被提交到国际标准化组织。 经过多次政治讨论之后，应一些主要的法国汽车厂商要求，增加了“Vehicle Area Network（VAN）”内容。并于 1993 年11月发布 ISO 11898 标准。除 CAN 协议外，它还标准化了一个物理层 - 速率高达1 Mbit/s。与此同时，在ISO 11519-2中，通过局域网传输数据的低功耗、容错方式也实现了标准化。由于标准的缺陷，这一点从未得到实施。 1995年，ISO 11898 标准通过附录进行了扩展，该附录描述了使用29位CAN标识符的扩展帧格式。
Unfortunately, all published CAN specifications and standardizations contained errors or were incomplete. To avoid incompatible CAN implementations, Bosch made sure (and still does) that all CAN chips comply with the Bosch CAN reference model. Furthermore, the University of Applied Science in Braunschweig/Wolfenbüttel, Germany, has been conducting CAN conformity testing for several years, lead by Prof. Lawrenz. The used test patterns are based on the internationally standardized test specification ISO 16845. Today, several test houses offer CAN conformance testing services.
遗憾的是，所有已发布的CAN规范和标准化都包含错误或不完整。 为了避免不兼容的CAN实施，Bosch 确保（现在仍然）所有CAN芯片都符合Bosch CAN参考模型。 此外，在 Lawrenz 教授的带领下，德国 Braunschweig /Wolfenbüttel 的 Applied Science 大学多年来一直在进行 CAN 一致性测试。使用的测试模式基于国际标准化的测试规范 ISO 16845。今天，一些测试机构也提供 CAN 一致性测试服务。
Revised CAN specifications have been standardized. ISO 11898-1 describes the ‘CAN data link layer’, ISO 11898-2 defines the ‘Non-fault-tolerant’ CAN physical layer’, and ISO 11898-3 specifies the ‘Fault-tolerant CAN physical layer’. ISO standards 11992 (truck and trailer interface) and 11783 (agriculture and forestry machines) both define CAN-based application profiles based on the US-protocol J1939, however they are not compatible.
修订后的 CAN 规范已经标准化。 ISO 11898-1 描述了’CAN数据链路层’，ISO 11898-2 定义了’非容错’CAN物理层’，ISO 11898-3 规定了’容错CAN物理层’。 ISO 标准11992（卡车和拖车接口）和11783（农业和林业机器）都基于美国协议 J1939 定义基于CAN的应用配置文件，但它们不兼容。
The time of the CAN pioneers CAN开拓者的时代
Although CAN was originally developed to be used in passenger cars, the first applications came from different market segments. Especially in northern Europe, CAN was already very popular in its early days. In Finland, the elevator manufacturer Kone used the CAN bus. The Swedish engineering office Kvaser suggested CAN as a communications protocol within machines to some textile machine manufacturers (Lindauer Dornier and Sulzer) and their suppliers. In this connection, under the leadership of Lars-Berno Fredriksson, these companies founded the ‘CAN Textile User’s Group’. By 1989, they had developed communication principles that helped to shape the development environment ‘CAN Kingdom’ in the early 1990s. Although CAN Kingdom is not an application layer with respect to the OSI reference model, it can be considered the ancestor of the CAN-based higher-layer protocols.
虽然CAN最初是为乘用车开发的，但CAN的第一个市场应用却来自于其他领域。 特别是在北欧，CAN早期就已经很受欢迎了。 在芬兰，电梯制造商Kone使用CAN总线。 瑞典工程办公室Kvaser建议CAN作为一些纺织机械制造商（Lindauer Dornier和Sulzer）及其供应商的机器内的通信协议。 在这方面，在 Lars-Berno Fredriksson 的领导下，这些公司成立了“CAN Textile User’s Group”。 到1989年，他们制定了沟通原则，以助于在20世纪90年代初塑造“CAN Kingdom”的发展环境。 虽然 CAN Kingdom 不是OSI参考模型的应用层，但它可以被认为是基于CAN的高层协议的原型。
In the Netherlands, Philips Medical Systems had joined the industrial CAN users by deciding to use CAN for the internal networking of their X-ray machines. The ‘Philips Message Specification’ (PMS), mainly developed by Tom Suters, represented the first application layer for CAN networks. Professor Dr. Konrad Etschberger from the University of Applied Science in Weingarten, Germany, had almost identical ideas. In the Steinbeis Transfer Center for Process Automation (STZP), which he was in charge of, he developed a similar protocol.
在荷兰，Philips医疗系统决定使用CAN构成X光机的内部网络，成为CAN的工业用户。 主要由 Tom Suters 开发的“飞利浦消息规范”（PMS）代表了CAN网络的第一个应用层。 来自德国 Weingarten 的 Applied Science 大学的Konrad Etschberger教授也持同样的观点。 在他负责的 Steinbeis 过程自动化转移中心（STZP）中，他开发了一个类似的协议。
In spite of the fact that the first standardized higher-layer protocols started to emerge, most CAN pioneers used a monolithic approach. Communication functions, network management, and application code were one piece of software. Even though some users would have preferred a more modular approach, they still would have had the disadvantage of a proprietary solution. The necessary efforts for enhancing and maintaining a CAN higher layer protocol had been underestimated – which is still partly true today.
尽管第一批标准化的高层协议开始出现，但大多数CAN先驱使用的是整体式方法。通信功能、网络管理和应用程序代码是一个软件。尽管有些用户更喜欢模块化的方法，但他们仍然有专有解决方案的缺点。增强和维护更高层协议的必要努力被低估了——这在今天仍然是部分正确的。
In the early 1990s, the time was right to found a user’s group to promote the CAN protocol and to foster its use in many applications. In January of 1992, Holger Zeltwanger, at that time editor of the VMEbus magazine (publisher: Franzis), brought users and manufacturers together to establish a neutral platform for the technical enhancement of CAN as well as the marketing of the serial bus system. Two month later, the ‘CAN in Automation’ (CiA) international users and manufacturers group was officially founded. In these early days, the CAN Newsletter was already published.
在20世纪90年代早期，是时候找到一个用户组织来推广CAN协议并促进其在许多应用中的使用。 1992年1月，当时 VMEbus 杂志编辑 Holger Zeltwanger（出版商：Franzis）将用户和制造商聚集在一起，为CAN的技术增强以及串行总线系统的营销建立了一个中立的平台。 两个月后，‘CAN in Automation’（CiA）国际用户和制造商集团正式成立。 在这之前，CAN 通讯已经发布。
The first technical publication, released after only a few weeks, was about the physical layer: CiA recommended using only CAN transceivers that comply to ISO 11898. Today, the manufacturer-specific EIA-485 transceivers, which were quite commonly used in CAN networks at that time and were not always compatible, should have completely vanished.
仅仅几周后发布的第一份技术出版物是关于物理层的：CiA 建议仅使用符合ISO 11898的CAN收发器。今天，那个时候在CAN网络中非常常用的制造商专用的并不总是兼容的EIA-485收发器应该已经完全消失了。
One of the first tasks of the CiA was the specification of a CAN application layer. Using the existing material from Philips Medical Systems and STZP, along with the help of other CiA members, the ‘CAN Application Layer’ (CAL), also called the ‘Green Book’, was developed. While developing specifications using CAN, one of the main tasks of the CiA was to organize the exchange of information between CAN experts and the ones who wanted to become more knowledgeable on CAN. Therefore, since 1994, the international CAN Conference (iCC) is held.
CiA的首要任务之一是规范CAN应用层。利用飞利浦医疗系统公司和STZP公司的现有材料，在其他CiA成员的帮助下，开发了“CAN应用层”(cal)，也称为“绿皮书”。在使用CAN开发规范时，CiA的主要任务之一是组织CAN专家和那些想对CAN有更多了解的人之间的信息交流。因此，从1994年起，CiA每年召开一次国际CAN会议（iCC）。
Another academic approach was pursued in the LAV: the German agricultural vehicle association. Since the late 1980s, a CAN-based bus system for agricultural vehicles (LBS) had been developed. But before the work could be successfully completed, the international committee had decided in favor of a US solution, J1939 (ISO 11783). This application profile, which is also based on CAN, was defined by the committees of the SAE Truck and Bus Association. J1939 is a non-modular approach that is very easy to use, but is also quite inflexible.
在LAV，还采用了另一种学术方法：德国农用车协会。 自20世纪80年代后期以来，已开发出基于CAN的农用车辆总线系统（LBS）。 但在成功完成工作之前，国际委员会已经决定采用美国的解决方案 J1939（ISO 11783）。 此应用程序配置文件也基于CAN，由SAE卡车和公共汽车协会的委员会定义。 J1939是一种非模块化的方法，非常易于使用，但也非常不灵活。
A standardization of CAN was also developed for trucks. The networking between truck and trailer is standardized as ISO 11992. This protocol is based on J1939 and must be used in Europe as of 2006. The trend for automotive vehicles goes toward OSEK-COM and OSEK-NM, a communication protocol and a network management. Both have been submitted for international standardization. Automotive builders however have been using proprietary software solutions so far.
针对于卡车的CAN的标准化也被开发完成。 卡车和拖车之间的网络被标准化为 ISO 11992。该协议基于J1939，必须在2006年在欧洲使用。汽车的趋势是 OSEK-COM 和 OSEK-NM，一种通信协议和网络管理 。 两者都已提交国际标准化。 然而，汽车制造商迄今为止一直在使用专有软件解决方案。
From theory to practice 从理论到实践
Of course, semiconductor vendors who implemented CAN modules into their devices are mainly focused on the automotive industry. Since the mid 1990s, Infineon Technologies (formerly Siemens Semiconductors) and Motorola have shipped large quantities of CAN controllers to European passenger car manufacturers and their suppliers. As a next wave, Far Eastern semiconductor vendors have also offered CAN controllers since the late 1990s. NEC came out with their legendary CAN chip 72005 in 1994, but in this case they were too early – the device was a no-go.
当然，将CAN模块应用到其设备中的半导体供应商主要集中于汽车行业。 自20世纪90年代中期以来，英飞凌科技（前身为西门子半导体）和摩托罗拉已向欧洲乘用车制造商及其供应商提供大量CAN控制器。 作为下一波浪潮，远东半导体厂商自20世纪90年代末开始提供CAN控制器。 NEC 在 1994 年推出了他们传奇的 CAN 芯片 72005，但在这种情况下它们还为时过早 - 该设备并不能投入使用。
Since 1992, Mercedes-Benz has been using CAN in their upper-class passenger cars. As a first step, the electronic control units taking care of the engine management were connected via CAN. In a second step, the control units needed for body electronics followed. Two physically separate CAN bus systems were implemented, connected via gateways. Other car manufacturers have followed the example of their peers from Stuttgart and now usually also implement two CAN networks in their passenger cars. Nowadays, they all implement multiple CAN networks in their vehicles.
自1992年以来，梅赛德斯 - 奔驰一直在他们的高级乘用车中使用CAN。 作为第一步，负责发动机管理的电子控制单元通过CAN连接。 在第二步中，遵循身体电子设备所需的控制单元紧随其后。 从而实现了两个物理上独立的CAN总线系统，通过网关连接。 其他汽车制造商也效仿他们来自斯图加特的同行，现在通常也会在他们的乘用车上实施两个CAN网络。 如今，他们都在车辆中实施多个CAN网络。
In the early 1990s, engineers at the US mechanical engineering company Cincinnati Milacron started a joint venture together with Allen-Bradley and Honeywell Microswitch regarding a control and communications project based on CAN. However, after a short while, important project members changed jobs and the joint venture fell apart. But Allen-Bradley and Honeywell continued the work separately. This led to the two higher layer protocols ‘DeviceNet’ and ‘Smart Distributed System’ (SDS), which are quite similar, at least in the lower communication layers. In early 1994, Allen-Bradley turned the DeviceNet specification over to the ‘Open DeviceNet Vendor Association’ (ODVA), which boosted the popularity of DeviceNet. Honeywell failed to go a similar way with SDS, which makes SDS look more like an internal solution by Honeywell Microswitch. DeviceNet was developed especially for factory automation and therefore presents itself as a direct opponent to protocols like Profibus-DP and Interbus. Providing off-the-shelf plug-and-play functionality, DeviceNet has become the leading bus system in this particular market segment in the US.
20世纪90年代初，美国机械工程公司 Cincinnati Milacron 的工程师与 Allen-Bradley 和 Honeywell Microswitch 一起成立了一家合资企业，负责基于CAN的控制和通信项目。 但是，过了没多久，重要的项目成员换了工作，合资企业就崩溃了。 但 Allen-Bradley 和 Honeywell 分别继续这项工作。 这导致两个更高层协议’DeviceNet’ 和 ‘智能分布式系统’（SDS），它们非常相似，至少在较低的通信层中是这样。1994年初，Allen-Bradley 将 DeviceNet 规范转变为 “开放式DeviceNet供应商协会”（ODVA），从而推动了 DeviceNet 的普及。 Honeywell 未能采用与SDS相似的方式，这使得SDS看起来更像是Honeywell Microswitch 的内部解决方案。 DeviceNet 是专为工厂自动化开发的，因此它本身就是 Profibus-DP 和 Interbus 等协议的直接对手。 DeviceNet 提供现成的即插即用功能，已成为美国这一特定市场领域的领先总线系统。
In Europe, several companies tried to use CAL. Although the CAL approach was academically correct and it was possible to use it in industrial applications, every user needed to design a new profile because CAL was a true application layer. CAL can be looked at as a necessary academic step to an application-independent CAN solution, but it never gained wide acceptance in the field.
在欧洲，有几家公司尝试使用CAL，尽管CAL方法在学术上是正确的，并且可以在工业应用中使用，但是每个用户都需要设计一个新的profile，因为CAL是一个真正的应用层。CAL可以看作是独立于应用程序的can解决方案的必要的学术步骤，但它从未在该领域获得广泛的接受。
Since 1993, within the scope of the Esprit project ASPIC, a European consortium lead by Bosch had been developing a prototype of what would become CANopen. It was a CAL-based profile for the internal networking of production cells. On the academic side, Professor Dr. Gerhard Gruhler from the University of Applied Science in Reutlingen (Germany) and Dr. Mohammed Farsi from the University of Newcastle (UK) participated in what was one of the most successful Esprit activities ever. After the completion of the project, the CANopen specification was handed over to the CiA for further development and maintenance. In 1995, the completely revised CANopen communications profile was released and within only five years became the most important standardized embedded network in Europe.
自1993年以来，在Esprit项目ASPIC的范围内，Bosch 领导的欧洲财团一直在开发CANopen的原型。 它是基于CAL的生产单元内部网络配置文件。 在学术方面，来自德国罗伊特林根 Applied Science 大学的 Gerhard Gruhler 教授和英国纽卡斯尔大学的 Mohammed Farsi 博士参加了迄今为止最成功的Esprit活动之一。 项目完成后，CANopen规范被移交给CiA进行进一步的开发和维护。 1995年，完全修订的CANopen通信配置文件发布，仅在五年内成为欧洲最重要的标准化嵌入式网络。
The first CANopen networks were used for internal machine communication, especially for drives. CANopen offers very high flexibility and configurability. The higher layer protocol, which has been used in several very different application areas (industrial automation, maritime electronics, military vehicles, etc.) has in the meantime been internationally standardized as EN 50325-4 (2003). CANopen is being used especially in Europe. Injection molding machines in Italy, wood saws and machines in Germany, cigarette machines in Great Britain, cranes in France, handling machines in Austria, and clock-manufacturing machines in Switzerland are just a few examples within industrial automation and machine building. In the United States, CANopen is being recommended for fork lifts and is being used in letter sorting machines.
第一个CANopen网络用于内部机器通信，尤其是驱动器。 CANopen提供非常高的灵活性和可配置性。 已经在几个非常不同的应用领域（工业自动化，海事电子，军用车辆等）中使用的更高层协议同时已被国际标准化为 EN 50325-4（2003）。 CANopen正在欧洲使用。 意大利的注塑机，德国的木锯和机器，英国的卷烟机，法国的起重机，奥地利的搬运机器以及瑞士的钟表制造机器只是工业自动化和机器制造中的几个例子。 在美国，CANopen被推荐用于叉车，并用于信件分拣机。
CANopen not only defines the application layer and a communication profile, but also a framework for programmable systems as well as different device, interface, and application profiles. This is an important reason why whole industry segments (e.g. printing machines, maritime applications, medical systems) decided to use CANopen during the late 1990s.
CANopen不仅定义了应用层和通信配置文件，还定义了可编程系统的框架以及不同的设备，接口和应用配置文件。 这是整个行业领域（例如印刷机，海事应用，医疗系统）决定在20世纪90年代后期使用CANopen的一个重要原因。
With DeviceNet and CANopen, two standardized (EN 50325) application layers are available, addressing different industrial automation markets. DeviceNet is optimized for factory automation and CANopen is especially well suited for embedded networks in all kinds of machine controls. This has made proprietary application layers obsolete; the necessity to define application-specific application layers has become history (except, perhaps, for some specialized high-volume embedded systems).
借助DeviceNet和CANopen，可以使用两个标准化（EN 50325）应用层，满足不同的工业自动化市场需求。 DeviceNet针对工厂自动化进行了优化，CANopen特别适用于各种机器控制中的嵌入式网络。 这使得专有应用层变得过时; 定义特定于应用程序的应用程序层的必要性已成为历史（可能除了一些专门的高容量嵌入式系统）。
Time-triggered communication 时间触发通信
In the beginning of 2000, an ISO task force involving several companies defined a protocol for a time-triggered transmission of CAN messages. Dr. Bernd Mueller, Thomas Fuehrer, and other Bosch employees, together with experts from the semiconductor industry and from academic research defined the protocol ‘Time-triggered communication on CAN’ (TTCAN).
2000年初，一个由多家公司参与的ISO工作组定义了一种用于定时发送CAN消息的协议。Bernd Mueller博士、Thomas Fuehrer和博世的其他员工，以及来自半导体行业和学术研究的专家，定义了“时间触发CAN通信”(TTCAN)协议。
This CAN extension enabled the time-equidistant transmission of messages and the implementation of closed loop control via CAN, but also the use of CAN in x-by-wire applications. Because the CAN protocol has not been altered, it is possible to transmit time-triggered as well as event-triggered messages via the same physical bus system. However, the automotive industry has not adopted TTCAN. Also, industrial users have rarely made use of the time-triggered protocol extension. They used synchronous transmission functions instead, specified in CANopen, so-to-speak a soft time-triggering method.
这种CAN扩展使消息的时间等距离传输和通过CAN实现闭环控制成为可能，而且还可以在x-by-wire应用程序中使用CAN。由于没有更改CAN协议，因此可以通过相同的物理总线系统传输时间触发的消息和事件触发的消息。然而，汽车行业还没有采用TTCAN。此外，工业用户很少使用时间触发的协议扩展。他们使用在CANopen中指定的同步传输功能，也就是所谓的软时间触发方法。
Approval by authorities
In the late 90s, several proprietary CAN-based safety protocols were invented. Survived has the Safetybus p by Pilz, Germany. In the year 1999, CiA started to develop the CANopen-Safety protocol, which has been approved by the German TÜV. After heavy political deputes in the standardization bodies, this CANopen extension (CiA 304) was internationally standardized in EN 50325-5 (2009).
在90年代后期，发明了几种基于CAN的专有安全协议。 幸存下来的是德国Pilz的Safetybus p。 在1999年，CiA开始开发CANopen-Safety协议，该协议已获得德国TÜV的批准。 经过标准化机构的重大政治支持，这个CANopen扩展（CiA 304）在EN 50325-5（2009）中得到了国际标准化。
DeviceNet uses the CIP Safety protocol extension. The CANopen framework for maritime applications (CiA 307) was approved by one of the leading classification societies worldwide, Germanischer Lloyd. Among other things, this specification defines the automatic switchover from a CANopen network to a redundant bus system. These functions are nowadays generalized and specified in the CiA 302 series of additional CANopen application layer functions.
DeviceNet使用CIP安全协议扩展。 CANopen海事应用框架（CiA 307）得到了全球领先的船级社之一Germanischer Lloyd的认可。 此外，该规范定义了从CANopen网络到冗余总线系统的自动切换。 这些功能现在已在CiA 302系列附加CANopen应用层功能中进行了概括和指定。
CAN FD development
At the beginning of 2011, General Motors and Bosch started the development of some CAN protocol improvements regarding higher throughput. The automotive industry suffered in particular when downloading increasing software packages end-of-line into the electronic control units (ECU). This time-consuming task had to be shortened by a higher performing communication system. The idea to increase the transmission speed of CAN by introducing a second bit-rate was not new. Several academics had published approaches since the beginning of 2000. But none of them were mature enough to convince carmakers. In cooperation with other CAN experts, Bosch pre-developed the CAN FD specification, officially introduced in 2012 on the 13th international CAN Conference in the Hambach Castle, Germany.
2011年初，通用汽车和博世开始开发一些有关更高吞吐量的CAN协议改进。 汽车行业尤其在将越来越多的软件包下载到电子控制单元（ECU）中时受到了影响。 这个耗时的任务必须通过更高性能的通信系统来缩短。 通过引入第二比特率来提高CAN传输速度的想法并不新鲜。 自2000年初以来，一些学者已经发表了一些方法。但它们都不够成熟，不足以说服汽车制造商。 博世与其他CAN专家合作，预先开发了CAN FD规范，于2012年在德国汉巴赫城堡举行的第13届国际CAN大会上正式推出。
During the standardization process within ISO, several academic weaknesses in the proposed error detection mechanisms were found. This required a review of the CAN FD protocol and the introduction of additional safeguards (e.g. stuff-bit counter). This is the reason why there is a non-ISO CAN FD protocol, which is incompatible to the ISO CAN FD protocol standardized in ISO 11898-1.
在ISO标准化过程中，发现了所提出的错误检测机制存在的一些学术缺陷。这需要对CAN FD协议进行审查，并引入额外的安全措施(例如填充位计数器)。这就是为什么有一个非ISO CAN FD协议，这是不兼容的在ISO 1188 -1中标准化的 ISO CAN FD协议。
Future of CAN
The future of CAN is bright. The lifetime of CAN technology might have been prolonged by 10 to 20 years with the introduction of the CAN FD protocol. The automotive industry has already started to adopt the CAN FD protocol for the next generation of in-vehicle networks. It can be expected that all future applications will make use of the CAN FD protocol. It doesn’t matter if they require higher bandwidth or not. You can still use CAN FD with a single bit-timing setting. The payload length is configurable from 0 to 64 byte anyway.
CAN的未来是光明的。 随着CAN FD协议的推出，CAN技术的寿命可能会延长10到20年。 汽车行业已经开始为下一代车载网络采用CAN FD协议。 可以预期所有未来的应用都将使用CAN FD协议。 它们是否需要更高的带宽并不重要。 您仍然可以使用单个位定时设置的CAN FD。 无论如何，有效载荷长度可配置为0到64字节。
CiA currently develops the CANopen FD protocol, which is based on the CAN FD lower-layers. In particular for industrial motion control application, higher transmission rates and longer payloads (up to 64 byte) are very welcome. CiA is also involved in the development of a CAN FD based application layer for commercial vehicles using the existing Parameter Groups as specified in the SAE J1939 series.
CiA目前开发了CANopen FD协议，该协议基于CAN FD低层。 特别是对于工业运动控制应用，非常受欢迎更高的传输速率和更长的有效载荷（高达64字节）。 CiA还参与使用SAE J1939系列中规定的现有参数组开发基于CAN FD的商用车辆应用层。
