Start of frame character selection for ADI

Rawley.Myers at Rawley.Myers at
Mon Nov 11 12:07:12 PST 2002

* From the T10 Reflector (t10 at, posted by:
* Rawley.Myers at

Rawley Myers
Principle Firmware Engineer
----- Forwarded by Rawley Myers/ENG/LMS/Plasmon on 11/11/2002 01:07 PM
                    Rawley Myers                                                                                                              
                    Sent by:             To:     10 at                                                                                   
                    Rawley Myers         cc:                                                                                                  
                    01:06 PM                                                                                                                  

This is in reply to following request

The ADI working group in T10 is in the process of developing a standard for
the interface between a Medium Changer type device and the Data Transfer
type device(s) (tape drives, optical disk drives, ...) that are mounted
within it.  The prevalent physical interface in use today without a
standard is RS-422.  The working group has decided that continued use of
this physical interface will allow for the most seamless transition to the
standardized interface.  This transition period will most likely include
devices that support both the standardized protocol and one or more legacy
protocols, sharing the same physical interface.  Devices may implement
algorithms to select the protocol to use though vendor specific means.  To
facilitate this capability, the ADI working group would like to select a
Start Of Frame byte that will not interfere with current protocols used on
this type of interface, if it is at all possible.

I have been tasked by the working group with putting together a
spread-sheet to facilitate the Start Of Frame byte selection process.  I am
soliciting feedback from companies that plan on using the ADP or ADT
standards in their products in an effort to avoid collisions with legacy
protocols.  This feedback should include a list of byte values that we
should avoid using, a list of byte values that are recommended, and/or a
list of byte values that are acceptable.  This data will be put into a
spread-sheet that will be published as a T10 proposal, so please don't send
me anything proprietary.  Feedback may be sent directly to me, or may be
posted to the T10 reflector.

The current serial interfaces implemented at Plasmon are -

- library serial interface for IBM LTO drives
- library/drive serial interface for UDO drive

Both of these interfaces use the standard STX (02 ASCII) and ETX (03 ASCII)
for start and end of packet respectively with character stuffing delimeters

Rawley Myers
Principle Firmware Engineer

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