Computer Organization Bus Structure popo Computer Organization Bus

Computer Organization, Bus Structure popo

Computer Organization, Bus Structure • A communication pathway connecting two or more devices • When a word of data is transferred between units all its bits are transferred in parallel • ie. The bits are transferred simultaneously over many lines, one bit per line. • A group of lines that serves as a connecting path for several devices is called a bus • A group of lines connected to different devices is called bus. • Bus can carry data and control signals • Single bus – simple way to interconnect functional units. popo

Computer Organization, Bus Structure • Single Bus Structure popo

Computer Organization, Bus Structure • • • • All units are connected to this bus Bus can used only for one transfer at a time So only 2 units can actively use the bus at any given time. Only one device at a time can successfully transmit. Single bus – low cost and It is flexible for attaching diff devices By using multiple bus simultaneously can transfer more than one data at a time This leads to increase the performance of the system. So the bus can carry several data at a time in parallel such as Power Instructions Data Addresses Commands popo

Computer Organization, Bus Structure • Multiple-Bus Organization • The following Figure shows a three-bus structure. • All registers are combined into a single block called register file with three ports: 2 outputs allowing 2 registers to be accessed simultaneously. • Buses A and B are used to transfer source operands to the A and B inputs of ALU, and result transferred to destination over bus C. popo

Computer Organization, Bus Structure popo

Computer Organization, Bus Structure • Diff units in a system having diff speed • Keyboard • Printer are relatively slow • some units are very fast all these devices communicate with each other over the same bus • in order to communicate all types of units smoothly include buffer registers with the devices to hold the data during transfer. • eg transfer of data between processor and printer • Processor sent data over the bus to printer buffer • Once the buffer is loaded the printer can start printing With out the interaction of the processor • The bus and processor are now free to do another work. popo