COMPUTER ORGANIZATIONS CSNB123 NSMS2013 Ver.1Systems and Networking1

COMPUTER ORGANIZATIONS CSNB123 Overview Input/Output devices: external / peripheral devices NSMS2013 Ver.1Systems and Networking2

COMPUTER ORGANIZATIONS CSNB123 Importance of Peripheral Devices Interaction between computer and the outside world – make it functional NSMS2013 Ver.1Systems and Networking3

COMPUTER ORGANIZATIONS CSNB123 I/O Modules Contains logic  perform communication function between the peripheral and the bus Interface to the system bus/central switch Control peripheral devices NSMS2013 Ver.1Systems and Networking4

COMPUTER ORGANIZATIONS CSNB123 Importance of I/O Module Varieties of peripheral devices  various operation  Not practical – burden the processor  Hard to control – data transfer rate is slower than processor and memory  Use different data formats and word lengths NSMS2013 Ver.1Systems and Networking5

COMPUTER ORGANIZATIONS CSNB123 Major Function of I/O Interface  to the processor and memory via system bus/central switch  to one/more peripheral devices NSMS2013 Ver.1Systems and Networking6

COMPUTER ORGANIZATIONS CSNB123 External Device (ED) ED connected to computer by a link to an I/O module Use of link;  Exchange; Status Control Data NSMS2013 Ver.1Systems and Networking7

COMPUTER ORGANIZATIONS CSNB123 Classification of ED NSMS2013 Ver.1Systems and Networking8

COMPUTER ORGANIZATIONS CSNB123 Interface to I/O Module NSMS2013 Ver.1Systems and Networking9

COMPUTER ORGANIZATIONS CSNB123 Interface to I/O Module (Cont.) NSMS2013 Ver.1Systems and Networking10 TermDescription Control logiccontrols the device’s operation Transducerconverts data; From electrical to other forms of energy (output) From other forms to electrical (input) Bufferrelated to transducer- hold data temporarily, size 8 to 16 bits

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module NSMS2013 Ver.1Systems and Networking11

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module (Cont.) To coordinate the flow of traffic between internal resources and ED E.g. data transfer from ED to CPU  Check device status - CPU ask I/O module  I/O module returns device status Ready – CPU request data  I/O module get data from ED  Transfer data NSMS2013 Ver.1Systems and Networking12

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module (Cont.) To communicate between internal resources and ED Operations;  Command decoding Accept command from CPU send to control bus  Data Exchange between CPU and I/O module over data bus  Status reporting Status of ED  Address recognition Know address for each I/O device NSMS2013 Ver.1Systems and Networking13

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module (Cont.) The I/O module must able to perform DC Operations;  Command  Data  Status information NSMS2013 Ver.1Systems and Networking14

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module (Cont.) Data comes from main memory in rapid burst and must be buffered by the I/O module, then send to the device at device’s rate NSMS2013 Ver.1Systems and Networking15

COMPUTER ORGANIZATIONS CSNB123 Categories of Major Function for I/O Module (Cont.) I/O module responsible for;  error detection Transmission error  report errors to the CPU NSMS2013 Ver.1Systems and Networking16

COMPUTER ORGANIZATIONS CSNB123 I/O Module Structure TermDescription System busConnect I/O module to the computer Data registersBuffer the in/out data into/from I/O module Status/Control registers Provide register’s status Control signal lines Allow I/O module logic interacts with CPU CPU issue command to the IO module Address linesKnow and generate device’s address External device interface logic Device interfaces to the device it’s control I/O channel / processor Handle detail processing burden I/O LogicUsed in primitive I/O module NSMS2013 Ver.1Systems and Networking17

COMPUTER ORGANIZATIONS CSNB123 Programmed I/O Direct Memory Access (DMA) Interrupt Driven I/O NSMS2013 Ver.1Systems and Networking18