The model I have is CD7220 and it is designed to show information about a customer purchasing in a nice blue-green colour onto a Vacuum Fluorescent Display with 2 rows and 20 columns.
I started to search for some documentation and found the datasheet then started to look inside to see how it was interfaced with the POS cashier machine.
The VFD is interfaced via RJ45 connector and from the signal perspective, a HIN232 circuit handle the conversion between RS232 serial COM port to TTL UART. Basically, this circuit is a clone of Maxim's MAX232 RS232<>TTL level convertor.Arduino NANO; the RTC is a DS1307.
The backup battery, a rechargable Li cell was dead and I replaced with a 5 V/4F capacitor. This is enough to keep the time for some time when power is off.
Because the circuits in the VFD need 24V, I put inside a DC/DC boost convertor so I can power the board with anything above 5V and below 24V. Yeah, I know, this is too big for this project but this was laying on my junk boxes here... You can use any boost DC/TS that can sustain 5W in a close box for extended periods of time.
To set the RTC actual Time and Date I used the example that came with the DS1307 library; just upload it into the Nano and start Serial monitor.
After setting the Time and Date as above, use the code provided on the Github, insert the correct UTC offset for your region and then upload the code to Arduino.
The code is commented and it is self explanatory; before you upload it, check the correct offset for UTC.