Colin,
It looks like you found this was a hardware issue.

To those looking at this post, there are a few things to remember when using a chip select area: (references are for LogicLoader )

1) Make sure no other devices are connected in this area and if so, make sure you take them into consideration: (e.g. Slow CS area, Fast CS area, .etc) If you were going to use the fast chip select area, you want to be very careful when changing the area bus settings. For example, if you tried to change the Fast chip select area from 16 to 32 bits wide, you would not be able to talk to the I/O Controller anymore and may freeze up the system. It is not recommended to change the areas Logic has set up for on board devices. (Flash, SDRAM, IO Controller [Fast/Slow], .etc)

2) Change the bus settings (Static Memory Controller) for the area to fit your devices needs. Check out the Sharp LH7A40x User Guide for more information. For example, if I wanted to set up Area 1 for 16 bits, I could use the following: w /w 0x80002004 0x1000fa60;

3) In LoLo, make sure the memory is mapped. You can check with the 'info cpu' command in LogicLoader. To map an area, use the 'remap' command, as Colin has used here.

4) When accesssing an area, keep in mine the bus width and the size of your accesses (reads/writes) If you do a 32 bit write to a 16 bit area, you will likely see unwanted results.