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

Write register content to a node.

Implementation must take care so all page register change done by these routines must restore the content of the page registers to there original content when they are done. 

 | Data byte | Description | 
 | :---------: | ----------- | 
 | 0 | Node address. | 
 | 1 | MSB of page where the register is located. | 
 | 2 | LSB of page where the register is located. | 
 | 3 | Register to write. | 
 | 4 | Content for register. | 
 | 5,6,7 | Optional extra data bytes to write. | 

A read/write response event is returned on success.

Event allows a register (or a maximum of four consecutive registers) located on any page can be written in a single operation.

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. | 
 | 16 | MSB of page where the register is located. | 
 | 17 | LSB of page where the register is located. | 
 | 18 | Register to write. | 
 | 19  | Content of register. byte 20-buffer-size Optional extra data bytes to write. | 
