可编程控制器三层网络解析.pptVIP

DeviceNet由开放式设备网供货商协会ODVA（Open DeviceNet Vendors Association）组织和管理，ODVA是一个负责DeviceNet协议的制定和增补工作的国际组织。 现有供货商会员316个，已开发了350多种DeviceNet产品。 DeviceNet产品增长势头迅猛，在美国和日本，它所占的市场份额已达50%以上，它每年正以高于150%的惊人速度不断增长 几乎所有世界著名的电器和自动化元件生产上都在大力开发DeviceNet产品，如ABB、Rockwell、Phoenix、Contacts、Omron、Hitachi、Cutler-Hammer等 * Power (24Vdc, 8A) Signal to all devices on a single cable! Termination resistors are 120 or 121 Ohms, 1/4 Watt or larger They MUST be placed at each end of the trunk line between white and blue wires. There are both open and sealed versions. Do not use carbon resistors!! Metal film is preferable. “Trunk” and “Drops” are topology terms. The trunkline is the “backbone” of your network. Drops serve as physical connection mechanisms to the trunkline. Drop length up to 20 feet. There are 4 types of cables: Thick, Flat (KwikLink) , Thin cable and Class 1 drop cable. Thick, Flat and Class 1 drop cables are rated for 8 amps of current. Class 2 thick cable, only 4 amps in North America. Thin cable is rated for 3 amps of current Thick, Flat and Thin cable can be used for “Trunk” Class 1 drop cable is designed only for drops. * 还有… 开放式连接 菊花链路连接方式 * There are 4 types of cables: Thick, Flat (KwikLink) , Thin cable and Class 1 drop cable. Thick, Flat and Class 1 drop cables are rated for 8 amps of current. Class 2 thick cable, only 4 amps in North America. Thin cable is rated for 3 amps of current Thick, Flat and Thin cable can be used for “Trunk” Class 1 drop cable is designed only for drops. * DeviceNet Cable DeviceNet Power, 8 Amps Max. * * 采用基于CAN的广播方式工作，网络上任一个节点均可在任一时刻主动向网络上其它节点发送信息，而不分主从。 (2) 网上可容纳64个节点地址，每个节点支持的I/O数量没有限制。 (3) 采用短帧结构，传输时间短，受干扰的概率低，具有极好的检错效果，具有CRC校验和其它检错措施，保证了数据出错率低。 (4) 通信介质为独立双绞总线，信号和电源承载于同一电缆。 (5) 支持设备的热插拔，无需网络断电。 (6) 采用非破坏性逐位仲裁机制，保证了通信的实时性。 * DeviceNet具体实例 * ControlNet最早于1995年10月面世。1997，7月由Rockwell等22家企业联合发起成立了ControlNet International 组织，Rockwell 公司把技术转让给了该组织。该组织是非盈利性的，主要负责推广、发展ControlNet技术，提供测试和组织培训等。 ControlNet Internatinal 组织也取得了很大的发展、，到目前成员公