The 82C55A is still available from Harris, Intel and others. It is more commonly used for expanding I/O rather than memory. The memory address bus is fixed in the architecture. The 82C55A can be used to add I/O for more Chip Selects, but something like a 4-16 line decoder may be a better solution. It is difficult to know without understanding your exact application, and I have not followed it. ----- Original Message ----- From: "Eisermann, Phil [Ridg/CO]" To: Sent: Thursday, April 15, 2004 9:17 AM Subject: Re: [EE:] Memory mapped I/O expander > 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. > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu