Another variant of the serial cable is the Duplex Serial Cable. This cable has a standard female DB25 connector on one end (transmitter) and a smaller male DB9 connector on the other end (receiver). This cable can handle either a DV12 system (for 2400 baud) or a high speed systems (for 9600 baud) down to 6400 baud. The cable is intended for transmitting and receiving data between two devices. The interface is exactly the same on the transmit and receive connectors.
A three-state serial cable is used to connect diagnostic equipment and software to target equipment such as a computer or a PLC. This cable is a 3-wire cable and consists of a transmit line, a receive line, and an optional ground line. The transmit line, the receive line, and the ground all have the same cable type connections and flat pins.
The transmit line is used for sending data to a host computer or other device. It may additionally be used to determine if the DTE and DCE serial connections are working. The receive line is used to receive information from a device. The receive line can be used to give feedback to the DTE device reporting if the device has successfully completed a transaction.
The optional ground line allows for a "higher" ground to be used on the DTE and DCE devices. An additional physical ground connection between these devices may not always be possible. This additional ground would provide a "substrate" for conducting noise to ground if both devices operate on the same electrical ground. Without a separate ground option on the DTE and DCE devices, there could be noise coupling back and forth between the devices.
The special data transmission mode on CD is used when inserting a UART into a RS232 connector. This mode allows transmission to take place without paying attention to the received data. Instead, the data is transmitted in a continuous state, and this signal can be received so long as the receiving device expects to receive data (or a parity bit). This function allows a user to read or write data without the need to pay attention to the lines which may contain data or instructions. d2c66b5586