•The microprocessor can be programmed to
perform functions on given data by writing specific instructions into its
memory.
–The microprocessor reads one instruction
at a time, matches it with its instruction set, and performs the data
manipulation specified.
–The result is either stored back into
memory or displayed on an output device.
The
8085 Architecture
•The 8085 uses three separate busses to
perform its operations
–The address bus.
–The data bus.
The
Address Bus
–16 bits wide (A0 A1…A15)
•Therefore, the 8085 can access locations
with numbers from 0 to 65,536. Or, the 8085 can access a total of 64K
addresses.
–“Unidirectional”.
•Information flows out of the
microprocessor and into the memory or peripherals.
–When the 8085 wants to access a
peripheral or a memory location, it places the 16-bit address on the address
bus and then sends the appropriate control signals.
The
Data Bus
–8 bits wide (D0 D1…D7)
–“Bi-directional”.
•Information flows both ways between the
microprocessor and memory or I/O.
–The 8085 uses the data bus to transfer
the binary information.
–Since the data bus has 8-bits only, then
the 8085 can manipulate data 8 bits at-a-time only.
The
Control Bus
–There is no real control bus. Instead,
the control bus is made up of a number of single bit control signals.