Re: PROBLEM: aic7xxx SCSI system hangs

From: Justin T. Gibbs (
Date: Thu Oct 11 2001 - 14:15:21 EST

>Sorry for my incomplete console output yesterday.

Not a problem.

Here's the interesting part...

>scsi0:0:2:0: Attempting to queue an ABORT message
>scsi0: Dumping Card State in Command phase, at SEQADDR 0xbf

The sequencer believes that the last, REQ qualified, phase was
the command phase.

>ACCUM = 0x80, SINDEX = 0xa0, DINDEX = 0xe4, ARG_2 = 0x0
>HCNT = 0xa

We're setup to send a 10byte cdb(command) to the target. No bytes of
the cdb have yet been transfered.

>SCSISEQ = 0x12, SBLKCTL = 0xa
> DFCNTRL = 0x24, DFSTATUS = 0x80

The data fifo is all set to send data...

>LASTPHASE = 0x80, SCSISIGI = 0x44, SXFRCTL0 = 0x80
But what's this? The target has us in data-in phase.

>SSTAT0 = 0x0, SSTAT1 = 0x3

But this phase, according to the hardware, was never qualified by
a REQ, so we never see this change and fall out of the loop that is
trying to process the command phase.

To sum up, from time to time, the controller sees the first REQ for
the data-in phase that follows the command phase, prior to seeing the
phase lines change to data-in. This is either caused by the plextor
not allowing the proper bus-settle time for the phase change to be
seen prior to asserting REQ *OR* your cabling is poor (too long,
marginal/bent pin, incorrect termination, etc.) giving a similar

As for why you cannot talk to the device after a while, the device
has been set offline. The controller was unable to talk to it
successfully, so the SCSI layer decided to ignore it.

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This archive was generated by hypermail 2b29 : Mon Oct 15 2001 - 21:00:40 EST