D96113r0

To:		pete_mclean@maxtor.com
Cc:		
Bcc:		
From:		colegrove@VNET.IBM.COM
Subject:	ABCD Jumper Memo in .TXT
Date:		Sunday, January 28, 1996  09:51:01 MST
Attach:		Headers.822
Certify:	N
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Pete, I may not be able to get this into Word format in time for the
mailing. I whacked out all the formatting codes and turned it into TXT.
Best Regards, DC
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January 22, 1996

To: X3T13

From: Daniel J. Colegrove
      IBM Corportation
      5600 Cottle Road
      San Jose CA 95193
      (408) 256-1978


Subj: Use of pins A-D on 44-pin connector

The ABCD jumper implementation on IBM Thinkpad systems and
IBM Travelstar drives allows drive address selection, cable
selection, and power up in standby mode.

The Thinkpad connector implementation is:

    No Jumper: Master (Device 0)
    A-B: Slave (Device 1)
    D-B: Cable Select
    C-A: Don't Care (Jumper Park)
    C:   Standby Mode Control Line

Pin electrical connection:
 o o . C A        A: tied up to +5V with 10K Ohm
 o o . D B        B: Open / Low  : Device 0
                     High        : Device 1
                  C: Open / High : Power on state = Idle
                     Low         : Power on state = Standby
                  D: Connected to pin 28 (Cable Select) and tied
                     up to +5V with 10K Ohm

While there are several ABCD pin implementations today,
causing selection of a standard configuration to be somewhat
arbitrary, the committee should take into consideration the
current system and drive implementations when selecting a
guideline for future design. The Thinkpad/Travelstar implementation
is well defined and in use today.