I/O port
An I/O port typically consists of four registers, called the status , control,data-in, and data-out registers.
| S.N. | Register & Description |
|---|---|
| 1 | Status RegisterThe status register contains bits that can be read by the host. These bits indicate states such as whether the current command has completed, whether a byte is available to be read from the data-in register, and whether there has been a device error. |
| 2 | Control registerThe control register can be written by the host to start a command or to change the mode of a device. For instance, a certain bit in the control register of a serial port chooses between full-duplex and half-duplex communication, another enables parity checking, a third bit sets the word length to 7 or 8 bits, and other bits select one of the speeds supported by the serial port. |
| 3 | Data-in registerThe data-in register is read by the host to get input. |
| 4 | Data-out registerThe data out register is written by the host to send output. |