The following image depicts the pin diagram of 8085 Microprocessor −
The pins of a 8085 microprocessor can be classified into seven groups −
Address bus
A15-A8, it carries the most significant 8-bits of memory/IO address.
Data bus
AD7-AD0, it carries the least significant 8-bit address and data bus.
Control and status signals
These signals are used to identify the nature of operation. There are 3 control signal and 3 status signals.
Three control signals are RD, WR & ALE.
Three status signals are IO/M, S0 & S1.
IO/M
This signal is used to differentiate between IO and Memory operations, i.e. when it is high indicates IO operation and when it is low then it indicates memory operation.
S1 & S0
These signals are used to identify the type of current operation.
Power supply
There are 2 power supply signals − VCC & VSS. VCC indicates +5v power supply and VSS indicates ground signal.
Clock signals
There are 3 clock signals, i.e. X1, X2, CLK OUT.
Interrupts & externally initiated signals
Interrupts are the signals generated by external devices to request the microprocessor to perform a task. There are 5 interrupt signals, i.e. TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. We will discuss interrupts in detail in interrupts section.
Serial I/O signals
There are 2 serial signals, i.e. SID and SOD and these signals are used for serial communication.
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