Use of 8255 programmable peripheral interface

[erece]

In 8085 nicroprocessor , we have 256 ports, which means we can connect 256 I/O devices with 8085 at a time (i'm not sure).
Then why do we use 8255 programmable peripheral interface to interface I/O devices with 8085 as it only has 3 ports??

 

[uart]

In 8085 nicroprocessor , we have 256 ports, which means we can connect 256 I/O devices with 8085 at a time (i'm not sure).
Then why do we use 8255 programmable peripheral interface to interface I/O devices with 8085 as it only has 3 ports??

You can have a lot more than 256 "ports" if you want to memory map them, but yes the 8085 processor has a separate 256 port (8 bit) I/O address space. The point however is that this is merely an address space, it's not a physical port implementation.

The 8255 port provides the physical logic (latches and handshaking logic) to implement efficient parallel I/O. Whether or not you choose to map the 8255 to the 8 bit I/O address space or to part of the regular 16 bit memory address space is completely up to you.