Lecture 10: Common Bus Architecture

Показать описание

#BusArchitecture
Common Bus System
The basic computer has eight registers, a memory unit, and a control unit. Paths must be provided to transfer information from one register to another and between memory and registers. The number of wires will be excessive if connections are made between the outputs of each register and the inputs of the other registers. A more efficient scheme for transferring information in a system with many registers is to use a common bus. It is known that how to construct a bus system using multiplexers or three-state buffer gates. The connection of the registers and memory of the basic computer to a common bus system.
The outputs of seven registers and memory are connected to the common bus. The specific output that is selected for the bus lines at any given time is determined from the binary value of the selection variables S2S1, and S0. The number along each output shows the decimal equivalent of the required binary selection. For example, the number along the output of DR is 3. the 16-bit outputs of DR are placed on the bus lines when S2 S1 S0 = 011 since this is the binary value of decimal 3. The lines from the common bus are connected to the inputs of each register and the data input of each register and the data inputs of the memory. The particular register whose LD (load) input is enabled receives the data from the bus during the next clock pulse
transition.