I had wrote on this subject last year and put the project down until now. I am having a problem when an external device sets its address lines to outputs while connected to the EZ-USB AN2125 chip at Port D. I an2125 goes into an unknown state. I am using the fast read and fast write on the an2125 and the fast write works just fine. When I attempt to do a fast read the the external device swithches to an output is when the an2125 loses control. Any help would be appreciated.
I guess I don't understand your comment. The micros never try to send at the same time. Does the data bus on the an2125 always act like an output? The an2125 code works as a stand alone and not on the development board.
All I know is the data bus is not shared with I/O pins. The 2125 manual state that the 2125 is the SOLE master of the memory expansion bus. I would talk to Cypress to see if what you are doing is OK.