Subject: RE: P1394> Re: SBP-2 Bidirectional ORB

From: Fumio Nagasaka <[email-masked]>
Date: Sat, 22 Nov 1997 02:10:42 +0900

In a message dated 97-10-06 22:13:42 EDT, [email-masked] writes:
> 1. I agree with David's observation that two ORBs (one read, one write) can
> be used instead of a bidirectional ORB.  A device is free to fetch both ORBs
> and execute them in whatever order it likes, including simultaneously.  A
> device or device class can mandate that such ORB pairs be provided, even
> though SBP-2 does not require it.

If the target device does not have any data to reply, when the initiator is keeping
Out-ORB, In-ORB and Out-ORB, the target fetch agent will be stalled at second
ORB and third ORB will not be consumed.

In this case, "AGENT_STATE" shall be ACTIVE at this moment. Thus if the initiator
try to ping DOORBELL, this write-transaction for DOORBELL is redundant. To 
overcome this state, the initiator need to write a value to AGENT_RESET register
to force "AGENT_STATE" to turn RESET state. Is this a normal job for this purpose?
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Fumio Nagasaka
Epson Software Development Laboratory Inc.
Tel +81 268 25 4111,  Fax +81 268 25 4627
E-mail to [email-masked]