I am using the XBYTE macro to access a memory mapped device. The chip select is being handled via another port (P1) to allow the full 64K of addresses to be axcessed. When I read data from the memory device I read 0x00 from addresses 0x00 - 0xFF. Above 0xFF the data reads correctly. I have verified that the memory device contains valid data in 0x00 - 0xFF address range. I also have scoped the RD line and it does appear that it is activated to read the data. Please let me know any thoughts. Thanks.
Are you sure that this meets the timing requirements of your memory-mapped thingy?