Received the first prototype PCB to expand the Arty. I've created a board which has 4 pmod connectors for 8 bit data, plus another connector which uses some more GPIO pins to handle upper 8bits plus other signals such as chip selects and the like.

It needed a bit of bodge wiring to the read/write signals due to a typo on my behalf (doh). 8 bit data works perfectly to 1 3.3v sram chip. The upper 8bits seem to be working ok with a decent cable length.

I've also added a DS1314 soic chip to provide a battery backup and warning led to maintain memory at shutdown. The board also breaks out the full bus to a 64pin expansion connector. I'll be using that to test various level shifters and other options.