**Mandatory.** Must be implemented by all level I devices.

Write register content to a node. 

*If a node have several pages with user defined registers Extended Register Write is a better choice to choose for writing as the page is also set when writing a register using that type. The standard registers can always be read without setting a page though as they are always mapped into the upper 128 bytes.*

 | Data byte | Description | 
 | :---------: | ----------- | 
 | 0 | Node address.         | 
 | 1 | Register to write.    | 
 | 2 | Content for register. | 

A read/write response event is returned on success.

The following format can be used for nodes on a Level II segment as a midway between a full Level II handling as specified in Class=1024 and Level I. 

 | Data byte | Description | 
 | :---------: | ----------- | 
 | 0-15 | GUID (MSB -> LSB). | 
 | 16 | Reserved. | 
 | 17 | Register to write.   | 
 | 18 | Content of register. | 
