Devices and Device Drivers Flashcards
A register is ?
a storage location associated with the I/O device that data can be read from and written to
The I/O controller ?
reads commands written to the control register and performs the requested action
The control register is ?
where the device driver writes commands such as read or write for the I/O controller to act upon
The data register is?
where the device driver writes data that the device outputs and reads data that the device inputs
A status register?
might indicate to the device driver whether the device is ready to accept a command, that the device is busy, or that an interrupt has occurred
the data registers might be supplemented by a first-in first-out (FIFO) chip, in which?
multiple bytes or words of input or output data are stored in the order they were received
Port-mapped I/O uses?
dedicated memory addresses, referred to as ports, and special CPU instructions to communicate with I/O devices
memory-mapped I/O?
the control and data registers are mapped into
the computer’s main memory space and the CPU uses the same instructions for reading and writing I/O registers as it does for reading and writing RAM
programmed I/O (PIO) devices
require the CPU to read and write each byte or word of data from and to the device registers
direct memory access (DMA)
transfer large blocks of memory to and from I/O devices with little involvement by the CPU
A DMA controller transfers data between?
the I/O device and a block of memory, allowing the CPU to attend to other tasks
Most I/O devices can be categorized based on?
−bHow data is accessed (randomly or sequentially)
− How much data is accessed – one byte per transfer or a block of data per transfer
A random-access device allows?
data accesses to occur directly at any location of the device’s storage, without having to start at the beginning each time a data access occurs
Sequential-access devices include ?
serial ports, network interfaces, and tape drives
a character-stream device
A device that transfers data one byte at a time
- Keyboards, mice, serial ports, and sound cards are examples
