8085 Microprocessor

8085 is a general purpose microprocessor having 40 pins and works on single power supply. To study the pin diagram we group
 the signals into 5 categories:

1.Power Supply
2.Clock Signals
3.Interrupt Signals
4.Address and Data bus
5.Control and Status signals
6.Serial I/O Port
7.DMA Request Signals




                     

Power Supply Signal and clock signal:
VCC:-Vcc is to be connected to +5V power supply.
Vss:-Ground reference
X1 and X2:- This pin is used for providing the clock frequency to the microprocessor. Generally Crystal oscillator or LC oscillator is used to generate the frequency. The frequency generated here is internally divided into two.As we know that the basic operating timing frequency of the microprocessor is 3 MHz so
6 MHz frquency is applied.


Serial Input Output port:-
SID and SOD:-These pins are used for serial data communication.


Interrupt Signal:-
Pin 6 to 11:- These pins are used for interrupt signals. Generally and external devices are connected here which requests the microprocessor to perform a particular task.

There are 5 pins for hardware interrupts-
TRAP, RST7.5, RST 6.5, RST5.5 and INTR
INTA is used for acknowledgement. Microprocessor sends the acknowledgement to external devices through the INTA pin.


Address Bus and DATA Buses:-
AD0-AD7:-These are multiplexed address and data bus. So it can be used to carry the lower order 8 bit address as well as the data. Generally these lines are demultiplexed using the Latch.
During the opcode fetch operation, in the first clock cycle the lines deliever the lower order address bus  A0-A7.
In the subsequent IO/M read or write it is used as data bus D0-D7. CPU can read or write data through these lines.

A8-A15:- These are address bus used to address the memory location.