pic microcontroller discussion list wrote:
> Hi,
>
> Is anybody aware of a 'ready to go' I/O expander that can be attatched
> to a standard async memory bus?? I know phillips/maxim etc do I2C and
> SPI  I/O expanders but I can`t recall seeing a device that would
> attatch to standard address/data bus.

the 82C55A was commonly used for this. Not sure if it is still made,
but I imagine there are similar upgraded devices today...

> I realise something could be
> knocked up with a couple of latches/some gates or some sort of
> programmable logic device but I was wondering if anything was
> available off the shelf first.

i suspect programmable logic has nowadays largely replaced these
types of special purpose chips. It's almost 'off-the-shelf' since
all you have to do is program it. Sorta like a PIC...

I run into this problem every once in a while so I'd be interested
in what you come up with.

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