Sending time on MODBUS TCP, setting MSB and LSB

Configuration
#1

My ventilation system doesn’t have a very accurate clock, but the time can be set using MODBUS. I’m trying to figure out how I can send the hour and minute in the following format:

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My current script looks like this:

alias: Komfovent set current time
sequence:
  - service: modbus.write_register
    data:
      address: 28
      hub: komfovent
      unit: 1
      value: "{{ now().timestamp() | timestamp_custom('%H%M') }}"

But this number, e.g. 1215, gets converted to hex as a whole, so the result becomes: 4BF, but the correct value should be 0C0F (0C = 12 and 0F = 15)

How can I do this with a template?

#2

Hopefully someone can help with a template, but if I could make a suggestion - why not do it in Node red? Would be easy to do and you could schedule a clock update for every 10 minutes or longer, depending on how badly your ventilation system drifts so you are not writing to that register every few seconds.

#3

My goal is not to write to the register every few seconds, but once a week. And that can easily be scheduled in Home Assistant as well.