SCAM Questions

John Lohmeyer jlohmeye at ncr-mpd.FtCollinsCO.NCR.COM
Wed May 4 08:41:30 PDT 1994

> Larry Lamers wrote:
> > 
> > 6)   Can we get rid of the abhorent terminology and used
> > SCSI terminology.
> > 
> > A SCAM master is really a SCAM initiator.  A SCAM slave is
> > really a SCAM target.
then Jon Buckingham wrote:
> My understanding of these definitions is this...
>    Master    : Controls iterations, i.e. transfers synchronisation
> 	       codes, function codes, action codes.
>    Slave     : participates in isolation stages in order to be
> 	       assigned an action code (typically an ID).
> 	       There may be several slaves participating at once.
>    Initiator : performs SCAM arbitration and selection (initiates SCAM
> 	       protocol). 
> 	       i.e. for level 1, is always the SCAM master.
> 		    for level 2, may be a master or slave.
> So the SCSI concept of initator and target doesn't really fit SCAM.
> Is this a correct interpretation?
> Jon Buckingham

I agree with Jon.  Master and Slave are separate concepts from Initiator
and Target.  However, I do expect that 99.44% of all Masters will also be
Initiators and 99.44% of all Slaves will be Targets.  Changing this terminology
would create more problems than it would solve.

Another point that bothers me in this thread is of mixing level 1 and 
level 2 SCAM masters on the same bus.  While I agree with others that this
is desirable, I feel that the best (perhaps only) way to make this work
is to require level 1 masters to recognize dominent master contention.  It
is not necessary for level 1 masters to initiate the dominient master
contention protocol, but they must react correctly if a level 2 master
initiates dominent master contention.  Perhaps, we should call such 
SCAM masters level 1.5.  They are mostly level 1, but they can be mixed
with level 2 SCAM masters.  


John Lohmeyer                      E-Mail:  John.Lohmeyer at FtCollinsCO.NCR.COM
NCR Microelectronics                Voice:  719-573-3362
1635 Aeroplaza Dr.                    Fax:  719-597-8225
Colo Spgs, CO 80916              SCSI BBS:  719-574-0424 300--14400 baud

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