产品细节介绍
XVC768102通道隔离卡件
Modbus的RTU版本包括每个传输的两字节CRC-16（16位循环冗余校验）。这个CRC-16算法基本上将整个数据流（仅数据位；忽略开始、停止和奇偶校验）视为一个连续的数据流
二进制数。该数字首先左移16位，然后除以特征多项式（1100000000000000101B）。除法的16位余数被附加到传输的末尾，首先是LSByte。这个结果消息（包括CRC）在接收器处除以相同的多项式时，如果否，将给出零余数发生传输错误。
如果369 Modbus从设备接收到CRC-16计算指示错误的传输，则从设备设备不会响应传输。CRC-16错误表示传输的一个或多个字节接收错误，因此应忽略整个传输，以避免369执行任何错误活动
CRC-16计算是用于错误检测的行业标准方法。这里包括一个算法来帮助程序员在没有标准CRC-16计算例程可用的情况下。用户可定义内存映射区369有一个强大的功能，称为用户可定义内存映射，它允许计算机使用一个Modbus数据包读取多达124个不连续的数据寄存器（设置点或实际值）。主计算机通常需要连续轮询每个连接的从属继电器中的各种值。如果这些值分散在存储地图，读取它们将需要多次传输，并会给通信链路带来负担。用户可对可定义内存映射进行编程，以将任何内存映射地址连接到连续用户映射块中的一个地址位置，以便可以通过读取这些连续的位置来访问它们。
用户可定义区域有两个部分：
1.包含125个实际值或设定点寄存器的寄存器索引区域（内存映射地址0180h-01FCh）地址。
2.寄存器区域（内存映射地址0100h-017Ch），包含寄存器索引中地址处的数据。
内存映射其余部分中分隔的寄存器数据可以重新映射到用户中的相邻寄存器地址可定义寄存器区域。这是通过在用户可定义的寄存器索引区域中写入寄存器地址来实现的。这允许改进数据的吞吐量，并可以消除对多个读取命令序列的需要。例如，如果需要从369读取平均相电流（寄存器地址0306h）和最热定子RTD温度（寄存器地址0.320h）的值
它们的地址可以重新映射如下：
1.使用功能代码06或16将0306h写入地址0180h（用户可定义寄存器索引0000）。
2.使用功能代码06或16将0320h写入地址0181h（用户可定义寄存器索引0001）。
寄存器0100h（用户可定义寄存器0000）的读取（功能代码03或04）将返回A相电流，寄存器0101h（用户定义寄存器0001）将返回最热定子RTD温度。
10.4.3事件记录器
369事件记录器数据从地址3000h开始。地址3003h是指向相关事件的指针（1表示最古老的事件和40代表最新的事件。要检索事件1，请将“1”写入事件记录选择器（3003h），然后读取3004h至3022h的数据。要检索事件2，请将“2”写入事件记录选择器（3003h）并读取数据从3004小时到3022小时。可以用这种方式检索所有40个事件。可以使用每个事件的时间和日期戳确保所有事件都已按顺序检索，而新事件不会破坏事件序列（事件1应该比事件2更新，事件2应该比事件3更新，等等）。
The RTU version of Modbus
includes a two byte CRC-16 (16 bit cyclic redundancy check) with every transmission. The CRC-16 algorithm essentially treats the entire data stream (data bits only; start, stop and parity ignored) as one continuous binary number. This number is first shifted left 16 bits and then divided by a characteristic polynomial (11000000000000101B). The 16 bit remainder of the division is appended to the end of the transmission, LSByte first. The resulting message including CRC, when divided by the same polynomial at the receiver will give a zero remainder if no transmission errors have occurred. If an 369 Modbus slave device receives a transmission in which an error is indicated by the CRC-16 calculation, the slave device will not respond to the transmission. A CRC-16 error indicates than one or more bytes of the transmission were received incorrectly and thus the entire transmission should be ignored in order to avoid the 369 performing any incorrect operation. The CRC-16 calculation is an industry standard method used for error detection. An algorithm is included here to assist programmers in situations where no standard CRC-16 calculation routines are available.
USER DEFINABLE MEMORY MAP AREA
The 369 has a powerful feature, called the User Definable Memory Map, which allows a computer to read up to 124 nonconsecutive data registers (setpoints or actual values) by using one Modbus packet. It is often necessary for a master computer to continuously poll various values in each of the connected slave relays. If these values are scattered throughout the memory map, reading them would require numerous transmissions and would burden the communication link. The User Definable Memory Map can be programmed to join any memory map address to one in the block of consecutive User Map locations, so that they can be accessed by reading these consecutive locations. The User Definable area has two sections: 1. A Register Index area (memory map addresses 0180h-01FCh) that contains 125 Actual Values or Setpoints register addresses. 2. A Register area (memory map addresses 0100h-017Ch) that contains the data at the addresses in the Register Index. Register data that is separated in the rest of the memory map may be remapped to adjacent register addresses in the User Definable Registers area. This is accomplished by writing to register addresses in the User Definable Register Index area. This allows for improved through-put of data and can eliminate the need for multiple read command sequences. For example, if the values of Average Phase Current (register address 0306h) and Hottest Stator RTD Temperature (register address 0320h) are required to be read from an 369,
their addresses may be remapped as follows:
1. Write 0306h to address 0180h (User Definable Register Index 0000) using function code 06 or 16. 2. Write 0320h to address 0181h (User Definable Register Index 0001) using function code 06 or 16. A read (function code 03 or 04) of registers 0100h (User Definable Register 0000) will return the Phase A Current and register 0101h (User Definable Register 0001) will return Hottest Stator RTD Temperature. 10.4.3 EVENT RECORDER The 369 event recorder data starts at address 3000h. Address 3003h is a pointer to the event of interest (1 representing the oldest event and 40 representing the latest event. To retrieve event 1, write ‘1’ to the Event Record Selector (3003h) and read the data from 3004h to 3022h. To retrieve event 2, write ‘2’ to the Event Record Selector (3003h) and read the data from 3004h to 3022h. All 40 events may be retrieved in this manner. The time and date stamp of each event may be used to ensure that all events have been retrieved in order without new events corrupting the sequence of events (event 1 should be more recent than event 2, event 2 should be more recent than event 3, etc.).
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