I am working with the MPC8641D (to be used as an RC device) and have some newbie confusion surrounding PCI Express usage and LAWs, ATMUs and BARs.
I read that LAWs map a region of 36 bit local address space to target interface. Does this mean they assign MPC8641 internal addresses to its internal 'peripherals’ (PCIe, RapidIO, etc etc) ? These are addresses on the so called “platform bus” ... absolutely nothing to do with the LBC or external address bus.
What then do ATMUs do ? I did see they “translate a 36 bit local address to an external address, or translate an external address to a 36 bit local address space”. What does “external address” refer to here ?
If LAWs and ATMUs are overlapping in some way, why are they both needed ?
I am getting all of this confused with ‘traditional’ PCI BARs, and am not sure who is who anymore.
I "see" things more clearly through graphical/pictorial representations .. any idea where I could find any ?