The reason for the Changes in Annex A

Aloisi, Paul aloisi at
Thu Apr 29 11:15:08 PDT 1999

* From the T10 Reflector (t10 at, posted by:
* "Aloisi, Paul" <aloisi at>


You asked about all the changes in Annex A, and wanted an explanation of

Table A.1 was changed to  include the  full voltage range of a normal signal
and 2 lines were added to show the ranges on wired Or-ed signals that could
have multiple drivers - current mode driving the line at one time.

A.2.1 Paragraph 3 was changed to increase the voltage range for the driver.
The change made when 99-127R4 increased the minim drive to 400 mA on
recommendation of the working group (originally I had asked for 350 mV
minimum) left the range too narrow for normal silicon processing. 400 - 640
mV is a very narrow range. The lower voltage was dropped to 375 mV and the
upper range was increased to 800 mV.    - Table A.2 and Figure A.2 reflects
this change too.

Table A.2 has the change above, plus a reduction in the common mode range.
Near the end of the SPI-2 development, the common mode range was reduced
|from +/- 500 mV to +/- 355 mV. Annex A was never corrected to reflect the
change. The common mode bias for the driver test were reduced to the +/- 355
mV plus the terminator common mode tolerance.

A.2.2 first paragraph reflects the same common mode change, which carries
over into figure A.4

Table A.3 had the wrong bias specified for the test. The bias is corrected
and the common mode voltage was reduced.

A.2.6 second paragraph is the same reduction in common mode.

A.3.1 is the same reduction in common mode which is also shown in Table A.6

A.4.1 has the wrong voltage range specified, it does not match Table 16, the
range should be removed. Table 16 defines the range for the type of

Sorry for the delayed response, I was off line for a couple of weeks.


Paul D. Aloisi
Unitrode    MS:84                                 Phone: 603-429-8687
7 Continental Blvd                                FAX: 603-429-8963
Merrmimack, NH 03054                       email: aloisi at

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