Port
From veswiki
The VES has four usable 8-bit data ports in the console, port 0 and 1 that are in the 3850 CPU and port 4 and 5 on one of the 3851 Program Storage Units.
Port 0
Bit 0-3 hooked to buttons TIME, MODE, HOLD, START
Bit 4 N/C
Bit 5
Bit 6 Enable signal to controllers
Bit 7 N/C
Port 1