CMSC 421: Exam 5 (100% Errorless Answers)

Device controller correct answers Electronic circuit capable of operating a specific I/O device using binary signals. Its interface is a set of hardware registers and flags, which may be set by and/or examined by device drivers. Device driver correct answers Device-specific program that implements I/O operations, requested by user applications or the OS, by interacting with the device controller. I/O system API instructions correct answers 1) Block-oriented devices (magnetic disks, CD ROMs, FLASH disks) 2) Character-oriented devices (keyboards, pointing devices, cameras, media players, printers) 3) Network devices (modems, Ethernet adapters) A generic interface to a device controller consists of... correct answers A set of registers Device controller registers correct answers Opcode, operands, busy, status, data buffer Opcode Register correct answers The register specifies the type of operation requested. Ex: read or write. Storing a new value into the register starts the I/O operation. Operands Register correct answers One or more operand registers are used to describe the parameters of the requested operation. The values are written by the CPU prior to starting the operation. Busy Register correct answers The register (a 1-bit flag) is set by the controller to indicate whether the device is busy or idle. Status Register correct answers The register is set by the controller to indicate the success or failure of the last I/O operation. Data Buffer Register correct answers The data buffer holds the data to be transferred between the device and main memory. Depending on the device type, the buffer may hold a single character or a block of data. Programmed I/O correct answers Style of I/O programming where the CPU, running the device driver, performs the copying of all data between the I/O device controller and main memory. Polling correct answers Technique to determine whether a device is busy or idle by reading a flag set and reset by the device controller. Direct Memory Access (DMA) correct answers Hardware component that allows devices to access main memory directly, without the involvement of the CPU.