Apple II
Technical Notes
_____________________________________________________________________________
                                                  Developer Technical Support

SmartPort
#5:    SCSI SmartPort Call Changes

Revised by:    Llew Roberts                                      January 1989
Written by:    Rilla Reynolds & Matt Deatherage                      May 1988

This Technical Note describes two CONTROL codes which have changed in revision 
C of the Apple II SCSI card firmware.
Changes since November 1988:  Added compatibility guidelines for future 
SCSI products.
_____________________________________________________________________________

Revision C of the Apple II SCSI card firmware includes two CONTROL code 
changes.

CONTROL code $04, previously defined as FORMAT, is now defined as EJECT.  This 
change reflects the revised SmartPort requirement that all devices maintain 
CONTROL code $04 as EJECT.  See SmartPort Technical Note #2, SmartPort Calls 
Updated, for more information.

CONTROL code $15 is now defined as FORMAT instead of RESERVED.  Note that 
there are two EJECT calls in this version, as CONTROL code $26 is still 
defined as EJECT.

To determine which version of the SCSI ROM is on any particular Apple II SCSI 
Interface Card, issue a $03 SmartPort STATUS call.  The revision C SCSI ROM 
will return the word $0200.  This does not follow the SmartPort Interface 
Version scheme described in SmartPort Technical Note #2.  However, future 
revisions of the Apple II SCSI card will follow this scheme.  Therefore, 
applications should expect any SmartPort SCSI firmware to behave as described 
in this Note if the version number is $0200 or if it is greater than or equal 
to $2000.

To maintain compatibility with future Apple II SCSI products, you should use 
the following guidelines:

o    Avoid access to the hardware or any RAM locations on the SCSI 
     card.
o    Do not use the Patch1Call, SetNewSDAT, or SetBlockSize control 
     calls.
o    For devices with a block size other than 512 bytes, use the 
     SmartPort Read and Write calls.  Do not use ReadBlock and 
     WriteBlock calls for these devices, since they only read or write 
     the first 512 bytes of a block.  The Read and Write calls may also 
     be used for devices with a 512-byte block size.
o    Never Reset the SCSI bus.

The Apple II SCSI Card firmware was designed to operate with SCSI CD-ROM and 
disk drives only.

Further Reference
_____________________________________________________________________________
o    Apple II SCSI Card Technical Reference
o    SmartPort Technical Note #2, SmartPort Calls Updated
