How Can We Set/Know 8255 Address

[murty_ind]

8255 address

hi guys,

i want to do interfacing 8255 with Atmel micro controller.
interfacing is thru memory mapped IO.
for intefacing 8255 we should know base address of 8255 na?
how can we know/set that base address

thanking u with anticipation

 

[Colbhaidh]

The 8255 has a Chip Select (pin 6 on the 40 pin version). Whatever address you decode to drive this CS pin low is the base address. Then the A0 and A1 pins address the relevant registers inside the 8255.
The 8255 chip itself does not need to know anything about its memory mapped address, it only knows that is the CS pin goes low, then someone is talking to it.