ModBus协议-功能码-0x0F

最新推荐文章于 2025-05-17 10:11:50 发布

Andy2019

最新推荐文章于 2025-05-17 10:11:50 发布

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分类专栏： ModBus协议文章标签： ModBus协议功能码

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本文详细介绍了Modbus协议中写多个线圈指令的功能和使用方法。该指令用于远程设备中设置一系列线圈的状态为ON或OFF，并通过请求数据字段指定具体的线圈地址及状态。文章还提供了一个实例，展示如何编写请求数据来控制指定范围内的线圈。

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15 (0x0F) Write Multiple Coils
This function code is used to force each coil in a sequence of coils to either ON or OFF in a remote device. The Request PDU specifies the coil references to be forced. Coils are addressed starting at zero. Therefore coil numbered 1 is addressed as 0. The requested ON/OFF states are specified by contents of the request data field. A logical ' 1' in a bit position of the field requests the corresponding output to be ON. A logical '0' requests it to be OFF. The normal response returns the function code, starting address, and quantity of coils forced.

Here is an example of a request to write a series of 10 coils starting at coil 20:The request data contents are two bytes: CD 01 hex (1100 1101 0000 0001 binary). The binary bits correspond to the outputs in the following way:
Bit: 1 1 0 0 1 1 0 1 0 0 0 0 0 0 0 1
Output: 27 26 25 24 23 22 21 20 – – – – – – 29 28
The first byte transmitted (CD hex) addresses outputs 27-20, with the least significant bit addressing the lowest output (20) in this set.The next byte transmitted (01 hex) addresses outputs 29-28, with the least significant bit addressing the lowest output (28) in this set. Unused bits in the last data byte should be zero–filled.