The N+ only stream out data
, that is it tells the uVGA (or other 4D screen) current temp is X and humidity Y and moon is Z etc.
The N+ also tells the uVGA the time and date.
The uVGA itself then is running a program I wrote (it is programmable using 4GL language) that split the screen to tiles, changes font sizes, colors and what have you. Icons and bitmaps are stored on SD card of the uVGA. That code and content of the SD is part of the ZIP file.
The N+ updates the uVGA only once in few minutes. In the mean time an internal timer on the uVGA is interrupting once a second so that you get a clock with seconds displayed.
Both N+ and uVGA have very inaccurate timing, but the N+ is slightly better. This is why the NTP is polled once in 6 hours and fixes the drifts of the N+ time, and then the N+ is also updating the uVGA.
The uVGA has two firmwares, the one I use that requires you to program in 4GL and another one that lets you send graphical commands from UART. Switching between the two is simple. Take a look at their site