MVI56-MCM (“Modbus 通訊模塊”) 產(chǎn)品可以讓 Allen-Bradley ControlLogix I/O 兼容處理器
輕松的和其它 Modbus 協(xié)議兼容設(shè)備取得通訊。兼容的設(shè)備不僅包括 Modicon PLC (都支
持 Modbus 協(xié)議)，還包括類別廣闊的終端設(shè)備。
MVI56-MCM 模塊是 Modbus 網(wǎng)絡(luò)和 Allen-Bradley backplane 之間的一個網(wǎng)關(guān)。來自于
ControlLogix 處理器的數(shù)據(jù)傳送異步于 Modbus 網(wǎng)絡(luò)上的數(shù)據(jù)活動。模塊內(nèi)部具有 5000 個
字的寄存器，用于處理器和 Modbus 網(wǎng)絡(luò)之間的數(shù)據(jù)交換。
以下討論包括一些概念，這些概念對于理解 MVI56-MCM 模塊的運(yùn)作是十分重要的。
上電時，模塊開始執(zhí)行以下邏輯功能：
1. 初始化硬件組件
a. 初始化 ControlLogix 背板驅(qū)動
b. 測試并復(fù)位所有 RAM
c. 初始化串行通訊端口
2. 等待來自于 ControlLogix 處理器的模塊配置
3. 初始化模塊寄存器空間
4. 在所選端口上，啟動從站驅(qū)動
5. 在所選端口上，啟動主站驅(qū)動

MVI56-MCM

當(dāng)模塊已經(jīng)接收來自處理器的模塊配置后，模塊會根據(jù)配置和網(wǎng)絡(luò)上的其它節(jié)點(diǎn)開始通
訊。
MVI56-MCM 模塊對 ControlLogix 背板使用方式是非常獨(dú)特的。通過背板，模塊使用自身
的輸入和輸出鏡像以分頁的方式，接收數(shù)據(jù)和發(fā)送數(shù)據(jù)到處理器。鏡像刷新的頻率取決于
用戶為模塊定義的計劃掃描頻率（scheduled scan rate）和模塊的通訊負(fù)荷。典型的刷新
頻率在 2 到 10 毫秒之間。
雙向的數(shù)據(jù)傳送是這樣實(shí)現(xiàn)的，模塊在其輸入鏡像中填充數(shù)據(jù)，再發(fā)送到處理器。梯形邏
輯程序把輸入鏡像中的數(shù)據(jù)放置在處理器的控制器標(biāo)簽（Controller Tags）中。模塊的輸
入鏡像是 250 個字。這個大型數(shù)據(jù)區(qū)讓數(shù)據(jù)在模塊和處理器之間快速的交換。

需要傳送到模塊的數(shù)據(jù)被處理器插放到模塊的輸出鏡像。模塊程序會把這些數(shù)據(jù)提取出
來，放置在模塊的內(nèi)部數(shù)據(jù)庫。模塊的輸出鏡像共有 248 個字。這個大型數(shù)據(jù)區(qū)讓數(shù)據(jù)在
模塊和處理器之間快速的交換。
下面的示意圖描述了在 ControlLogix 處理器，MVI56-MCM 模塊和 Modbus 網(wǎng)絡(luò)之間數(shù)據(jù)
移動的方式。

MVI56-MCM

The MVI56-MCM (” Modbus Communication Module “) product enables Allen-Bradley ControlLogix I/O compatible processors
Easily communicate with other Modbus protocol compatible devices. Compatible devices include not only Modicon PLC (all branches
With Modbus protocol), also includes a broad category of terminal devices.
The MVI56-MCM module is a gateway between the Modbus network and the Allen-Bradley backplane. Be from
The data transfer of the ControlLogix processor is asynchronous to data activity on the Modbus network. There are 5000 modules inside the module
Word register for data exchange between processor and Modbus network.
The following discussion includes some concepts that are important to understanding the operation of the MVI56-MCM module.
When the module is powered on, the following logical functions are performed:
1. Initialize hardware components
a. Initialize the ControlLogix backplane driver
b. Test and reset all RAM
c. Initialize the serial communication port
2. Wait for the module configuration from the ControlLogix processor
3. Initialize the module register space
4. Enable the slave driver on the selected port
5. On the selected port, start the primary station driver
When the module has received the module configuration from the processor, the module will start to communicate with other nodes on the network according to the configuration
Message.
The MVI56-MCM module is unique in its use of the ControlLogix backplane. Through the backplane, the module uses itself
The input and output mirrors in a paging manner, receiving data and sending data to the processor. The frequency of image refresh depends on
The scheduled scan rate defined by the user for the module and the communication load of the module. Typical refresh
The frequency is between 2 and 10 milliseconds.
Bidirectional data transfer is implemented in such a way that the module fills the data in its input image and sends it to the processor. Trapezoidal logic
The assembler places the data in the input image in the Controller Tags of the processor. Module output
It’s like 250 words. This large data area allows data to be exchanged quickly between modules and processors.

The data that needs to be sent to the module is plugged into the output image of the module by the processor. The module program will extract the data
To place in the module’s internal database. The output image of the module contains 248 characters. This large data area keeps the data in
Fast exchange between modules and processors.
The following diagram depicts data between the ControlLogix processor, the MVI56-MCM module, and the Modbus network
The way it moves.

MVI56-MCM