In order for computers to correctly transfer CNC programs to and from CNC machines, the cables need to be adequetely connected. This means that at least 3 (sometimes 5) pins of the computer I/O connector have to be connected to the correct pin of the CNC I/O connector.
Parity, data bits, stop bits, and baud rate have to be the same in both computer and CNC machines. G-ZERO uses even parity, 7 data bits, and 1 stop bit. When these are set incorrectly, garbled information will be transferred.
Information flow can be controlled by the way cables are connected. Software flow control is setup by connecting only pins for data communication. Hardware flow control (handshake) will require connecting the "request to send" and "clear to send" pins. The quality of transmission depends on different factors such as quality and length of the cables, amount of interference (RF and EMF noise), and CNC machine grounding.