A KCS cassette interface is similar to a modem connected to a serial port. Both connect to Serial Port 1. It can also connect to a serial port. It sends ASCII data using a serial port. The order of bits is not usually configurable within the serial port interface. The most typical devices plugged into the serial port were modems and mice. Additional memory and serial port expansion options were available from aftermarket companies. It can also be used with local serial port connections. Most models also have a connector for serial port access. They were standalone units that connected to any device with an asynchronous serial port. Two computers or applications can communicate through an emulated serial port link. A virtual serial port is an emulation of the standard serial port. Bit 4-6&colon; Clock Timing Control for serial port operation. The normal read and write calls on a serial port receive and send data bytes. These are stand-alone UART devices, similar to computer serial port peripherals.