Introduction
Bus Transfer is the most efficient way to transfer data. The data transferred in the bus transfer is collected using bus lines. Similarly, the transfer of data from the memory unit to the outside environment and vice versa is known as memory transfer.
Bus Transfer
- In a digital system of registers, a path must be provided to move information.
- Suppose separate lines are used between each register and all other registers in the system. In that case, the number of wires connecting all of the registers will be excessive because we are connecting each register with another register.
- A bus structure will not require an excessive connection. Thus it is very useful in transferring information.
- A bus is made up of a collection of common lines, one for each bit of a register, that are used to transfer binary data one by one.
There are two methods in bus transfer:
- Bus transfer using Multiplexer
- Bus transfer using Three states bus buffer
Bus Transfer using multiplexer
We can generate a common bus using a multiplexer. Multiplexer helps us choose the source register to put the binary data on the bus. Control Signal controls the input and output gating.
In the above figure
- Ri is the register. Rin and Rout are its input and output gating signals of Register Ri, respectively. When Rin is set to 1, the data is loaded into the register bus Ri. When Rout is set to 1, the data of the register bus Ri is loaded into the register bus.
- Z is the register, and Zin and Zout are the input and output gating signals of Register Z.
- Similarly, Y is the register and Yin and Yout are the input and output gating signals of Register Y.
Bus Transfer using three-state buffer
- We can also generate a bus system using three-state gates instead of multiplexers.
- Three State Buffer helps us generate a common bus.
- Here the three-state gates are similar to the digital circuit having three gates. Here the first two are similar to having logic 0 and 1. The third gate is in a state of high impedance.
Figure showing three-state buffer
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