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PCI arbiter doubt in REQ signal

No. Grant can go away anytime the arbiter decides. The current master only has to give up control of the bus after GNT is removed *and* its latency timer runs out.

FRAME# and GNT# have nothing to do with each other. REQ# causes GNT#, somewhere down the line and a master without a GNT# must give up the bus somewhere down the line (after it's latency timer runs out and *it* parks the bus), but other than theat they aren't related.

Get the spec, or perhaps more easily understood, the MindShare book.

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  Keith
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Keith
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Hi all,

I have got a doubt in PCI arbiter operation . Assume that a particular device issues a REQ(REQ0) and GRANT(GRANT 0) is issued to that particular deivce , that device pulls the FRAME signal low indicating it is using th PCI bus.Now during the entire duration for which the FRAME signal is low GRANT(GRANT 0) should be held low for that particular device.

My doubt is if in the FRAME low held duration if any other device issues a REQ (i.e pulls it low and again pulls it high before the FRAME has gone high.IS this a valid request OR does the REQ line need to be held until the GRANT is issued to that particular device.

Thanks in advance, Praveen

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praveen.kantharajapura

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