Pin Configuration of 8085 (cont.)

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6. Interrupts and Externally initiated operations:

• They are the signals initiated by an external device to request the microprocessor to do a particular task or work.
• There are five hardware interrupts called,

                                                       

• On receipt of an interrupt, the microprocessor acknowledges the interrupt by the active low INTA (Interrupt Acknowledge) signal.
• Reset In (input, active low)
• This signal is used to reset the microprocessor.
• The program counter inside the microprocessor is set to zero.
• The buses are tri-stated
• Reset Out (Output)
  • It indicates CPU is being reset.
  • Used to reset all the connected devices when the microprocessor is reset.
  
  

READY (input)

• Memory and I/O devices will have slower response compared to microprocessors.
• Before completing the present job such a slow peripheral may not be able to handle further data or control signal from CPU.
• The processor sets the READY signal after completing the present job to access the data.
• The microprocessor enters into WAIT state while the READY pin is disabled.

7. Single Bit Serial I/O ports:

• SID (input)            -  Serial input data line
• SOD (output)        -  Serial output data line
• These signals are used for serial communication.