🚀 go-pugleaf

Rich wrote:
>
> I am working on a small project involving a large number of digital
> ins and outs.  I have been looking at using a couple of Intel 8255s,
> but was wondering if there are any better options out there.
>
> Thanks for any info.
>
> Richard
>
> --
> ri...@earthlink.net

Basically no.  Though these parts are old, they're really pretty good.
There are modern, faster, CMOS, etc versions of these parts, but they're
the same 8255 chip.  Being able to program input, outputs and irq is
pretty nice.  The downsides to these parts is that they're big, somewhat
expensive in low volumes and can't sink/source much on their outputs.

Some other options might be:
1. If the I/O's are spread out, just use 74xx574's for outs and
74xx540's for inputs.  These are octal jelly bean parts that are very
cheap.  There are even transciever versions if you need to get fancy.

2. Several companies make big version of these bus parts in widths to
20+ bits which can make things simpler.  Check out Pericom and National.

3. You could use a medium sized FPGA to get lots of I/O.  It would
certainly not be as cheap as an 8255 but you could put some custom stuff
in it like address decoding, power up defaults, etc.  Something like an
Altera 7064 is pretty cheap and has a fair amount of I/O.

4. You might consider using a hybrid approach with a small FPGA routing
signals to 74XX574's etc.


Good Luck,
John