Bus

BUSes:-

1.What is an Address Bus?
         The Address bus is unidirectional i.e. information flows in one direction only from microprocessor to device only.microprocessor uses this bus to identify peripherals or memory locations.The memory locations or peripheral is identified with the binary numbers called as address.8085 consist of 16 address line hence it can address up to 2^16=65536 locations or 64K locations

We can find that how much memory location it can using the formula 2^N. where N is the number of bits used for 

address lines. 

So If a processor has 4 GB memory then,

         4GB= 4 * 1GB

         4 = 2^2
        
         1GB = 2^30
        
          4GB = 2^2   *   2^30 = 2^32

          So 32 address lines are required to access the 4 GB memory.

2.What is a Data Bus?

          8085 has 8-bit data bus.so it can be used to carry data from ooH to FFH (here H means Hexadecimal) This data bus is group of lines used for transferring data to and from microprocessor.Data Bus is bi-directional in nature i.e. data in between microprocessor ,peripheral and memory microprocessor uses this data bus to perform  second function i.e. transfer the data.

3.What are control bus?

          This control Bus comprises of various single lines that carry synchronization signal. The microprocessor uses such lines to perform third function i.e providing the timing signal.the different control signal generated are Memory read, Memory write, I/O read, I/O write, ready etc. This signals is used to identify the device type with which the microprocessor wants to communicate.