PM864AK02控制处理器
时间同步
时间同步消息是高优先级广播类型的消息。NIS模块立即为该消息类型提供服务。时间同步提供了一个通用的系统时基，用于排序异常报告、访问趋势数据和在系统控制台上显示。多播包含多个目的地数据的消息是多播消息。此邮件可以有一个到64个目的地。NIS POLL NIS轮询消息是单个目标消息。NIS模块使用此消息类型轮询另一个节点的操作状态。消息格式消息作为信息帧存在。每个帧由信息字段后面的消息控制字段组成。信息字段包含消息数据。它可以由多条消息组成，大小不一，最大可达1500字节。控制字段包含发起时间、序列、源、大小、循环计数、消息类型、目的地和校验和值。NIS模块递增所有传入消息的循环计数字段。当消息计数字段达到256时，将丢弃下一条消息。这有助于将重试和虚假消息流量降至最低。NIS模块使用消息类型确定如何处理消息。校验和和循环冗余校验码字段验证数据完整性。
信息传输
任何NIS模块都可以在任何时候传输消息，而不考虑系统上任何其他NIS模块的活动。每个NIS模块可以同时发送和接收消息。NIS模块的启动或关闭是本地的，不需要与INFI-NET循环上的其他NIS模块进行交互。每个NIS模块接收所有传入消息，并以存储转发方式将新的消息流传输到下一个节点。当NIS模块没有要发送的消息时，NIS模块将发送标志字符（空包）作为循环同步条件，以保持接收器处于锁定状态。NIS数据完整性NIS模块使用三种方法确保数据完整性。它们是重试逻辑、节点状态表和轮询。重试逻辑如果在第一次消息传输时，NIS模块没有从目标节点接收到肯定或否定的确认，则它会重新发送十一次消息。如果在这一系列重试之后仍然没有响应，则目标节点被标记为脱机，并且NIS模块将否定确认通知其他通信模块。节点状态表NIS模块维护一个系统范围内状态的内部表，例如脱机和忙碌节点。NIS模块将节点状态更改中继到其他通信模块。当NIS模块定期轮询节点时，它会相应地更新此表
TIME SYNCHRONIZATION
The time synchronization message is a high priority broadcast type of message. The NIS module services this message type immediately. Time synchronization provides a common system time base to be used for sequencing exception reports, accessing trend data, and display on a system console. MULTICAST A message that contains data for multiple destinations is a multicast message. This message can have from one to 64 destinations. NIS POLL The NIS poll message is a single destination message. The NIS module uses this message type to poll the operational status of another node. MESSAGE FORMAT Messages exist as frames of information. Each frame consists of a message control field that follows an information field. The information field contains the message data. It can consist of multiple messages and vary in size to a maximum of 1,500 bytes. The control field contains time of origination, sequence, source, size, circulation count, message type, destinations, and checksum value. The NIS module increments the circulation count field of all incoming messages. When a message count field reaches 256, the next message is discarded. This is useful in keeping retry and spurious message traffic to a minimum. The NIS module uses the message type to determine how to process the message. The checksum and cyclic redundancy check code fields verify data integrity.
MESSAGE TRANSMISSION
Any NIS module can transmit a message at any time without regard to the activities of any other NIS module on the system. Each NIS module can transmit and receive messages simultaneously. NIS module start-up or shutdown is local and requires no interaction with other NIS modules on the INFI-NET loop. Each NIS module receives all incoming messages and transmits a new stream of messages in a store and forward fashion to the next node. When there are no messages for the NIS module to transmit, the NIS module transmits flag characters (null packets) as the loop synchronizing condition to keep the receivers in lock. NIS Data Integrity There are three methods the NIS module uses to insure data integrity. They are retry logic, node status table, and polling. RETRY LOGIC If on the first message transmission the NIS module does not receive a positive or negative acknowledgment from the destination node, it retransmits the message eleven times. If after this series of retries there is still no response, the destination node is marked off-line and the NIS module informs other communication modules of the negative acknowledgment. NODE STATUS TABLE The NIS module maintains an internal table of system wide status's such as off-line and busy nodes. The NIS module relays node status changes to other communication modules. When the NIS module periodically polls nodes, it updates this table accordingly
产品优势
1：国外专业的供货渠道，具有价格优势
2：产品质量保证，让您售后无忧
3：全国快递包邮
4：一对一服务
公司主营范围简介
PLC可编程控制器模块，DCS卡件，ESD系统卡件，振动监测系统卡件，汽轮机控制系统模块，燃气发电机备件等，优势品牌：Allen Bradley、BentlyNevada、ABB、Emerson Ovation、Honeywell DCS、Rockwell ICS Triplex、FOXBORO、Schneider PLC、GE Fanuc、Motorola、HIMA、TRICONEX、Prosoft等各种进口工业零部件、欧美进口模块。
产品广泛应用于冶金、石油天然气、玻璃制造业、铝业、石油化工、煤矿、造纸印刷、纺织印染、机械、电子制造、汽车制造、塑胶机械、电力、水利、水处理/环保、锅炉供暖、能源、输配电等等
