Module 2
Interfacing of 8085
1. How do you interface 8085 with 8255?
Step 1:
A0-A7 is the Lower- order of 8-bit address separated from AD0-AD7 using
address latch/buffer for example IC 74373 and ALE signal.
The separated address lines A0-A7 are connected to A0-A7 input pins of 8255 and
the separated data bus D0-D7 are connected to D0-D7 pins of 8255.
Reset out of 8085 is connected to reset pin of 8255.
Step 2:
8255 does not have internal separate control logic generator, hence the IO/
,
and
control signals are not connected directly to 8255. These pins are
given first to decoder and decoded using 3:8 decoder
for example: IC 74138.
and
are connected to
and
input
of 8255.
Step 3: