MPC8315 local bus

[kennethhuang]

I may be confusing between the MPC8315 local bus and the local access windows, but how do I access the 2GB maximum local access window of an MPC8315 with its 26-bit local bus?  Thanks.

[Bulat]

1. All local access windows of the MPC8315 are identical, besides the local bus this includes also PCI, PCIe and DDR. We did not "artificially" reduce windows size for the local bus. However you do not have to set LAW size to 2GB, there are many other options that can better fit your particular configuration. Note also that you can put several local bus memory banks into one LAW.

2. 26-bit addressing is not a strict restriction. Note that UPM supports address multiplexing like in SDRAM devices. So theoretically the user is able to address memory space greater than 64MB using less than 26 address signals.

Regards,

Bulat

[kennethhuang]

So the local access windows allow you to have up to 2GB windows, but not for the local bus, which is limited to 64MB?

[Bulat · Accepted solution]

Basically yes. Note, the local bus is not limited to 64MB, this limitation of one Chip Select on the local bus.

Regards,

Bulat