CertiGuide to A+ (Core Hardware)  9  Chapter 0111:  Peripheral Devices       9  III  Peripheral Device Interfaces

III  Peripheral Device Interfaces 1 Asynchronous Versus Synchronous

Serial communication is the simplest form of data transfer in modern PC. In serial data transfers, data is sent one bit at a time, single file. As you learned in previous chapters, data is transferred between two devices inside of the computer using a bus. The analogy we used to describe this transfer was that of a highway. This highway could have multiple lanes and travel at various speeds. You can think of serial communications as being a one-lane road. Only one car is allowed to travel down the road at a time.

In modern PCs, serial communications are full duplex, meaning that both of the communicating devices can send data at the same time. This is opposed half duplex, in which only one other device can send data at a time. Full duplex communications are like that of a telephone call. Both parties on the line are able to talk same time. Half duplex communications are like that of the CB radio. In order for one party to transmit they must hold down a button and talk. The other party must listen to what they say and are unable to talk at the same time.

III  Peripheral Device Interfaces 1 Asynchronous Versus Synchronous