32.8 External Memory Mapping

The SMC provides up to 23 address lines, A[22:0]. This allows each chip select line to address up to 8 Mbytes of memory.

If the physical memory device connected on one chip select is smaller than 8 Mbytes, it wraps around and appears to be repeated within this space. The SMC correctly handles any valid access to the memory device within the page (see the figure below).

A[22:0] is only significant for an 8-bit memory, A[22:1] is used for a 16-bit memory.