What is PPI device and use of it in microprocessor 8085?

PPI device stands for Programmable Peripheral Interface. So as name suggest it can be used to interface any input output device with microprocessor. The 8255 chip is an example of a PPI device.

Now question is why it needed for interfacing with 8085 microprocessor?

If we look on microprocessor 8085 pin diagram then we found that it has no dedicated pin for interface input output device directly so we need some extra device to make interface with microprocessor 8085. For this reason 8085 is introduce to interface between microprocessor and input output device. 8255 also provide three ports Port A, Port B Port C. And we can interface Input output device at a time. 

Now here i give you the internal architecture and pin diagram of 8255 which will clear your doubt on how it works.

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