Why has the CF-Interface its own bus?

[Altera_Forum]

Hello, 

 Why has the CF-Interface its own “Avalon Tri-State Bridge”? Isn’t it possible to connect the CF-Interface to the “Avalon Tri-State Bridge” of the ext_ram_bus for saving some IO-Pins? Which advantages does the own “Avalon Tri-State Bridge” have?  Bye, niosIIuser

[Altera_Forum]

The CF interface was designed as a separate component and not just a tri-state component because of the need for some custom logic (additional control registers, etc.) to be included for some of the required functionality (power on/off, insertion/removal interrupt, etc.). 

 It's not possible to connect the CF interface to the ext_ram_bus because on the Altera development boards, the CompactFlash slot does not share pins with this bus. It actually shares pins with one of the Santa Cruz connectors.  It is, however, possible to create a CF interface component that uses a tri-state bridge. I did so for a customer's custom board. I modeled the class.ptf file after the flash and sram components. I created 2 slaves (one for each CF chip select line), changed the timing to that required by the CompactFlash, modified/added the signal names and then indicated which lines were shared with other tri-state components using the ptf assignments "shared=1" or "shared=0". Finally I removed all the gui configuration stuff as this component wasn't configurable. The board was then designed to share quite a few pins (address, data, read, write).  Dennis Microtronix Datacom

[Altera_Forum]

Hello Dennis, 

 Thank you for your reply.  I forgot to explain that I consider sharing the CF-Signals with the ext_ram_bus in a new design and not with the development board (sure that’s not possible). So it is possible to save some IOs in a new design. I hope there’s no timing problem when handling data from the Ethernet controller and the CF.  Bye, niosIIuser