topic Re: MPC8315 local bus in PowerQUICC Processors

MPC8315 local bus

kennethhuang — Wed, 15 Jul 2015 18:30:43 GMT

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.

Re: MPC8315 local bus

Bulat — Thu, 16 Jul 2015 06:59:02 GMT

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

Re: MPC8315 local bus

kennethhuang — Fri, 17 Jul 2015 18:02:16 GMT

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

Re: MPC8315 local bus

Bulat — Mon, 20 Jul 2015 13:53:10 GMT

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

Regards,

Bulat