[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: BURST Xactions CROSSING BAR BOUNDARIES



The original question refers to a BURST transaction in which the master
crosses the BAR boundary.  This isn't related to address decoding since
presumably the address is decoded to be within the target's assigned
memory space.  I couldn't find anything in the 2.1 spec which defined a
required response by a target if a burst transaction crosses a BAR
boundary.  There are several ways to respond to this situation but I
wasn't able to find any rules that defined a response.

For what it's worth I don't think that this situation calls for a hardware
solution.  Applications should never issue transfer requests which will
cross a BAR boundary.  The proposed response may not work too well since
the transfer was continued across the boundary by the time the
application/device driver terminates the transaction. 

Stuart.

 On Thu, 23 Jan 1997, Mark Gonzales wrote:

> 
> If the target does not disconnect exactly at the boundary, it will 
> claim data phases intended for some other pci target. This will 
> result in data corruption, and a system crash. 
> 
> If a target is mapped to a range of addresses, it must claim 
> addresses within that range, and ignore addresses outside that range.
> 
> I'm not sure why anyone would think that a computer system with 'fuzzy'
> imprecise address decoding would ever work. Am I misunderstanding your
> question?
> 
> --Mark
> not speaking for Intel
> 
> kands@usa.net writes
> >
> >Hi,
> >
> >It is not very clear in the specs of PCI2.1 regarding the BURST Xactions
> >Crossing BAR BOUNDARY.
> >
> > Let me be more exact on the problem. Suppose a Master Starts a Posted
> >Memory Xaction close the BAR BOUNDARY and during the Xaction crosses the
> >Boundary, Is it a must that the PCI target must issue a disconnect when
> >the Master crosses the Boundary or is it O.K if the PCI target takes
> >care by signalling to the application (the actual target where the write
> >was targeted) that the Master has crossed the boundary, and leaving the
> >responsiblity to the application to detect this condition and to issue
> >a disconnect to the target which whill in turn be reflected to the PCI
> >bus after say two clocks after the Master has crossed the BAR Boundary.
> >
> >If it is a must that the target has to disconnect exactly at the BAR
> >Boundary, Pls. let me know where it has been specified in the specs.
> 
> 


w