Asynchronous and Synchronous Communication Serial data transfers depend on accurate timing in order to differentiate bits in the data stream. The terms asynchronous and synchronous are slightly misleading because both kinds of communication require synchronization between the sender and receiver. Asynchronous communication is the prevailing standard in the personal computer industry. Asynchronous communication is a protocol for coordinating serial data transfers. Asynchronous execution refers to the capability of a device driver to carry out background processing.
Serial endpoints support both asynchronous communication and asynchronous execution.
Open Transport serial endpoints do not support synchronous communications protocols. However, they do support synchronous clocking supplied by an external device. Handshaking Methods for Flow Control Because a sender and receiver can't always process data at the same rate, some method of negotiating when to start and stop transmission is required. Open Transport serial endpoint providers support two methods of controlling serial data flow, known as handshaking. One method relies on the serial port hardware, the other is implemented in software.