1. 介绍
CAN 只定义物理层和数据链路层， 没有规定应用层，本身并不完整，需要一个高层协议来定义CAN 报文中的 11/29 位标识符、8 字节数据的使用。而且，基于 CAN 总线的工业自动化应用中， 越来越需要一个开放的、标准化的高层协议：这个协议支持各种 CAN 厂商设备的互用性、互换性，能够实现在CAN网络中提供标准的、统一的系统通讯模式，提供设备功能描述方式，执行网络管理功能。
![](https://wkrtcs.bdimg.com/rtcs/image?w=452&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"452","h":"446","dataType":"png","c":"word/media/image1.png","imgOriW":526,"imgOriH":519})
2. 对象字典(OD)
对象字典是一个有序的对象组，每一个对象组采用一个16位的索引和一个8位的子索引来寻址。
the Object Dictionary serves as an interface between the communication and the application.
![](https://wkrtcs.bdimg.com/rtcs/image?w=462&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"462","h":"292","dataType":"png","c":"word/media/image2.png","imgOriW":811,"imgOriH":513})
对象字典中索引的分类
![](https://wkrtcs.bdimg.com/rtcs/image?w=626&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"626","h":"241","dataType":"png","c":"word/media/image3.png","imgOriW":949,"imgOriH":365})
![](https://wkrtcs.bdimg.com/rtcs/image?w=580&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"580","h":"332","dataType":"png","c":"word/media/image4.png","imgOriW":936,"imgOriH":535})
![](https://wkrtcs.bdimg.com/rtcs/image?w=583&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"583","h":"398","dataType":"png","c":"word/media/image5.png","imgOriW":720,"imgOriH":491})
3. NMT状态机
![](https://wkrtcs.bdimg.com/rtcs/image?w=586&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"586","h":"361","dataType":"png","c":"word/media/image6.png","imgOriW":771,"imgOriH":475})
![](https://wkrtcs.bdimg.com/rtcs/image?w=547&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"547","h":"165","dataType":"png","c":"word/media/image7.png","imgOriW":1093,"imgOriH":330})
服务 | 预操作(Pre-Operational) | 操作 （Operational） | 停止 （Stopped） |
过程数据对象(PDO) | 否 | 是 | 否 |
服务数据对象(SDO) | 是 | 是 | 否 |
同步报文(SYNC) | 是 | 是 | 否 |
紧急报文(EMCY) | 是 | 是 | 否 |
网络管理(NMT) | 是 | 是 | 是 |
1.
2.
3.
3.1. 心跳报文(Heartbeat)
一个节点可以被配置为心跳报文的生产者，Heartbeat的消费者一般是主站
![](https://wkrtcs.bdimg.com/rtcs/image?w=531&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"531","h":"78","dataType":"png","c":"word/media/image8.png","imgOriW":531,"imgOriH":78})
![](https://wkrtcs.bdimg.com/rtcs/image?w=553&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"553","h":"170","dataType":"png","c":"word/media/image9.png","imgOriW":588,"imgOriH":181})
3.2. NMT Boot-up
NMT-Slave发布Boot up 报文通知NMT 主节点它已经从initialising状态进入pre-operational状态
![](https://wkrtcs.bdimg.com/rtcs/image?w=551&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"551","h":"113","dataType":"png","c":"word/media/image10.png","imgOriW":568,"imgOriH":116})
3.3. 节点保护/寿命保护
NMT主节点发送远程帧
![](https://wkrtcs.bdimg.com/rtcs/image?w=335&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"335","h":"85","dataType":"png","c":"word/media/image11.png","imgOriW":335,"imgOriH":85})
NMT从节点响应远程帧
![](https://wkrtcs.bdimg.com/rtcs/image?w=552&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"552","h":"68","dataType":"png","c":"word/media/image12.png","imgOriW":649,"imgOriH":80})
数据部分包括一个触发位（bit7），触发位必须在每次节点保护应答中交替置“0”或者“1”。触发位在第一次节点保护请求时置为“0”。位 0 到位 6（bits0～6）表示节点状态，可为下表中的数值。
![](https://wkrtcs.bdimg.com/rtcs/image?w=429&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"429","h":"290","dataType":"png","c":"word/media/image13.png","imgOriW":429,"imgOriH":290})
带*号的只有在支持Bootup的节点才提供，状态0不在节点保护应答中出现，因为节点在此状态下不应答节点保护报文。
4. 周期性过程数据(PDO)
![](https://wkrtcs.bdimg.com/rtcs/image?w=588&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"588","h":"343","dataType":"jpeg","c":"word/media/image14.png","imgOriW":692,"imgOriH":408})
![](https://wkrtcs.bdimg.com/rtcs/image?w=582&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"582","h":"342","dataType":"png","c":"word/media/image15.png","imgOriW":668,"imgOriH":398})
传输方式
1、 事件驱动
当输入值发生变化时，数据立即被发送出去
2、 远程请求
PDO由远程帧触发，大部分设备不支持远程帧，且CIA组织不推荐使用。
3、 同步传输
RPDO:先接收到数据，但不更新到设备，只有接收到同步帧出发后，才更新，通过这种方式实现同步。
TPDO:可以设置接收到多少个同步帧后才发送TPDO。
5. 非周期性服务数据(SDO)
建立在客户端与服务器这样一种模型之上。
操作可分为下载和上传。
1.
2.
3.
4.
5.
5.1. 加速传输
![](https://wkrtcs.bdimg.com/rtcs/image?w=545&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"545","h":"86","dataType":"png","c":"word/media/image16.png","imgOriW":939,"imgOriH":148})
![](https://wkrtcs.bdimg.com/rtcs/image?w=549&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"549","h":"59","dataType":"png","c":"word/media/image17.png","imgOriW":946,"imgOriH":102})
![](https://wkrtcs.bdimg.com/rtcs/image?w=552&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"552","h":"552","dataType":"png","c":"word/media/image18.png","imgOriW":581,"imgOriH":581})
5.2. 分段传输
主要用于传输超过32位的数据。
![](https://wkrtcs.bdimg.com/rtcs/image?w=490&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"490","h":"578","dataType":"png","c":"word/media/image19.png","imgOriW":445,"imgOriH":525})
5.3. 块传输
与分段传输的主要区别是其将数据划分成几个单一的包，在连续的请求或者应答中逐块的的传输这些包。可以在最后一段中发送CRC校验和。
6. 同步数据(SYNC)
![](https://wkrtcs.bdimg.com/rtcs/image?w=551&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"551","h":"166","dataType":"png","c":"word/media/image20.png","imgOriW":734,"imgOriH":221})
7. 紧急报文(EMCY)
![](https://wkrtcs.bdimg.com/rtcs/image?w=551&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"551","h":"96","dataType":"png","c":"word/media/image21.png","imgOriW":697,"imgOriH":122})
COB-ID:0x080+Node_ID
1003h中存放了错误的记录。
![](https://wkrtcs.bdimg.com/rtcs/image?w=455&md5sum=482b96bbe07ee5342c2be52e7e4e8dfc&sign=3e06f01631&rtcs_flag=1&rtcs_ver=3.1&l=webapp&bucketNum=84&ipr={"t":"img","w":"455","h":"697","dataType":"png","c":"word/media/image22.png","imgOriW":367,"imgOriH":562})
8. 设备描述文件（EDS）
以电子表格的形式呈现
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