To draw an entire screen full of data, the user code would wait until the television display reached the right side of the screen and update the registers for the playfield and player/missiles to correctly reflect the next line on the display.
To draw an entire screen full of data, the TIA periodically called an interrupt when the television display reached the right side of the screen. The user code would respond to the interrupt by updating the registers for the playfield and player/missiles to correctly reflect the next line on the display.