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8085 Bus Organisation

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The various units of a microprocessor are connected by three sets of parallel conducting lines called buses.

There are three buses in microprocessor:
  • Data bus
  • Address bus
  • Control bus
8085 Bus Organisation

Data Bus: 

  • 8085 microprocessor has 8-bit data bus. This means that it can carry the 8-bit data starting from 00H to FFH.
  • It is bidirectional. This means that these lines are used to flow data in both the directions. Data can be transferred or received through these lines.
  • It also connects the I/O ports and CPU.
  • It has 8 parallel lines of data bus i.e. it can access upto 2^8 = 256 data lines.

Address Bus:

  • 8085 microprocessor has 16-bit address bus.
  • The CPU sends the address of the memory location over this bus.
  • So the address bus carries the address of the memory location on which data is to written or from which data is to read.
  • It is unidirectional. This means that these lines are used to flow data only in one direction i.e. from microprocessor to peripheral devices.
  • It can access upto 2^16 = 64kB of memory location.

Control Bus:

  • Control bus is used for sending control signals from the microprocessor to memory and I/O devices.
  • These control signals enable the outputs of addressed memory devices and I/O devices.
  • Some important control signals are: memory read, memory write, I/O read, I/O write.
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