SMBus
FAQ Contents
|
This page contains answers to common
questions about the SBS If and the specifications contained here. There
are answers to questions about specific design topologies along with some tips
and tricks that we have found useful and presented here as
questions.
|
How do I join
the forum?
|
Join this forum through the System Management
Interface Forum, at the present time. Click on the link just following
this answer. This link takes you to a download site where you can obtain
copies of the Membership Application and an Adopters Agreement. Download
both forms in either PDF or Word format.
Send the completed forms to the address shown at
the end of the form. Send your first year's membership dues with the
Forum Membership Application.
|
How do I submit comments to the specification?
|
To comment on the SMBus specification, send mail
(click on the link) to: smbus@sbs-forum.org. Note that on
page ii of the specification is the e-mail address of the SMBus
Working Group reflector. The best way to comment is to send an e-mail to
that address. You may also send comments to me and I will route them to
the authors. Click on this link to send an e-mail to the Webmaster.
|
What's new
in revision 1.1 of the SMBus specification?
|
Description
|
Section
|
The specification was re-written to
clarify many implementation issues and requirements. Section numbers in
revision 1.0 do not correspond to those in revision 1.1. |
All |
The revision 1.1 document is is a
stand-alone specification that can be used for SMBus device design
independently from the I2C bus. |
All |
Packet Error Checking (PEC) is
added to Write Byte, Write Word, Write Block, Read Byte, Read Word and Read
Block protocols. If implemented, the protocols insert one byte calculated with
a CRC-8 after the last data byte. |
7.4, 7.5 |
Some error recovery methods are
described if a transmission error is detected. |
7.4, 7.7 |
AC Electrical Specifications:
No changes exist in the specification between rev 1.0 and rev. 1.1 pertaining
to AC electrical specifications. There is added clarity in the correct
use and interpretation of bus timeouts. There is a sub-section showing
alternative bus pull-up methods. |
8.1 |
DC Electrical Specifications:
VIL, MAX = 0.8 V (0.6 V in rev.
1.0)
VIH, MIN = 2.0 V (1.4 V in rev. 1.0)
ILEAK, MAX = ±5 µA (±1 µA in rev.
1.0) |
8.2 |
|
What is the
CRC-8 polynomial for SMBus?
|
The CRC-8 polynomial used in SMBus revision 1.1
is
C(x) = 1 0000 0111. Refer to the specification for protocol
usage.  Click on this link to view a CRC-8 Calculator.
Another handy link and reference to the cyclic
redundancy checking for CRC-8 is provided through one of the SBS IF Promoters
at http://semtech.com/support/design_crc.asp
|
|
|