Apple II
Technical Notes
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                                                  Developer Technical Support

SmartPort
#5:    SCSI SmartPort Call Changes

Revised by:    Matt Deatherage & Llew Roberts                   November 1990
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 January 1989:  Added notes about the Apple II High-Speed SCSI
Card.
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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
returns 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.  The Apple
II High-Speed SCSI Card returns version $3000 (3.0).

To maintain compatibility with the Apple II High-Speed SCSI Card and future
SCSI products, you should use the following guidelines when programming with
the revision C card:

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; however, the Apple II High-Speed SCSI Card works with most
SCSI devices, including removable drives, scanners, and tape backup units.

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