[SOLVED] 8255 interfacing with P89V51RD

[muthuece12]

hello sir,
i am doing a project, in that i am using P89V51rd2. in this project i need to interfacing 8255 and ir. i tried lot of programs but the output of the 8255 is not changing. i did not connect the 8255 as a external memory device.

my connection details:
microcontroller=8255
P1=d0-d7;
rd=rd;
wr=wr;
P3.5=a1;
P3.4=a0;
P3.3=cs;

plz can anyone help for the issue. thanks in advance

 

[IanP]

i did not connect the 8255 as a external memory device.

Then you have to re-create all conditions that the 8255 was designed to work with.
Also, you can't use MOVX instructions but rather go step-by-step.
First, set data on D0-D7 (you may need pull-up resistors -10k - on all 8 data lines), then address on A0 and A1, you can connect CS on the 8255 permanently to "GND", then generate the /RD or /WR cycle by pulling the related P3.X from H-to-L and back L-to-H ........

All of that can be done much, much easier with 737-latch, as described in this app-note:
**broken link removed**

I don't ask for reasons - but it's like re-inventing a wheel ...

:wink:
IanP

 

[muthuece12]

hello sir, thanks for giving the guide.now its working. thanks a lot sir.