Do you have a particular microprocessor in mind when asking the question? Some microprocessors have dedicated address bus and data bus while others have a portion of their address bus and data bus multiplexed.
actually we have just started with buses and they were teaching us the definitions.
And system bus was defined as "The same bus is used to carry address, data & control signal then it is known as system bus "
And this is what is said about multiplex bus "If the same bus is used to carry address as well as data (not at a time), then it is known as multiplex bus ".
I dont see any difference in their definitions....
To use PCs as an example: PCI-E vs. AGP vs. PCI. PCI-E is parallel-serial, AGP is a direct parallel bus with extra control lines, PCI is a shared bus. AGP would fall into "System", as would maybe PCI. PCI-Express doesn't fit neatly into either definition as it has aspects of both, but in a parallel-serial format.
With the varieties and speeds of serial, parallel, and hybrid buses, it's pretty difficult to narrow them into two types.
If "Data and Address" was clarified as being system address/memory/control, or peripheral address/memory/control, that would help remove confusion with the definitions.