Write in "UCHAR4" format by Modbus with function 16

I need to write a password on a device in "UCHAR4" format by Modbus with function 16.
This is the memory map of the variable:

I have configured a tag with this OPC item path to write to that address. It's right?

[device]1.HRS168:4 (The password is made up of 4 characters)

Best Regards.

Meh, maybe. Don't know what UCHAR4 means or if it matches the String behavior of the Modbus driver, which I think tries to write empty spaces at the end if you don't provide a String of the full length.

You'll have to try it and see.