Appendix E

Conformance

This appendix contains recommendations on conformance statements to this 
standard.

E1.  Alternatives

This standard contains various alternatives that are mutually exclusive within 
a system.

  (1)  Single-ended or differential drivers.
  (2)  Termination power supplied by the cable or not.
  (3)  Parity implemented or not.
  (4)  "Hard" RESET or "soft" RESET.
  (5)  Reservation queuing implemented or not.

E2.  Levels of Conformance

  By specifying which alternatives (listed above) are implemented, an 
environment is created enabling different features to be implemented.  These 
features are divided into three nested minimum levels as shown in Table E1.

                                   Table E1
                            Levels of Conformance

==============================================================================
Level        Initiator                           Target
------------------------------------------------------------------------------
  0     Accept COMMAND COMPLETE        Implement the mandatory commands   
        message.                       of section 7.                      
                                                                          
        Accept GOOD and CHECK          Implement the mandatory commands   
        CONDITION status codes.        of the supported device type(s).   
                                                                          
                                       Implement the COMMAND COMPLETE     
                                       message.                           
                                                                          
                                       If messages other than COMMAND     
                                       COMPLETE are implemented, then     
                                       implement MESSAGE REJECT message   
                                       also.                              
                                                                          
                                       Implement GOOD and CHECK CONDITION 
                                       statuses.                          
------------------------------------------------------------------------------
  1     Same as above plus             Same as above.
        ARBITRATION phase.
------------------------------------------------------------------------------
  2     Same as above plus             Same as above plus implement the
        accept DISCONNECT,             MESSAGE REJECT and IDENTIFY messages
        MESSAGE REJECT,                and implement all extended commands
        IDENTIFY, and SAVE             in section 7 and for the supported
        DATA POINTER messages          device type(s).
==============================================================================
E3.  Options

E3.1  Optional Commands.  This standard specifies a number of additional 
commands that can be implemented in each level.  Some of these commands, if 
implemented, require the implementation of other optional commands, messages, 
or both.  In this case, these additional commands, messages, or both shall 
also be implemented.

E3.2  Optional Messages.  This standard specifies a number of additional 
optional messages that may be implemented at any level.

E3.3  Other options.  Within some commands, additional features, called 
"options", are described.  These options need not necessarily be implemented.

E4.  Statement of Conformance

Any statement of conformance to this standard should declare which of the 
alternates listed in section E1 and which of the three conformance levels are 
implemented.  In addition, it should indicate which of the options listed in 
section E3 are implemented, if any.  In the case of optional messages, the 
conformance statement should state whether the message is generated, accepted, 
or both.

  If the synchronous data transfer option is implemented, any statement of 
conformance should so indicate and state both the maximum REQ/ACK offset and 
the minimum transfer period implemented.




























