Download System Management Bus (SMBus) Specification , version 3.

System Management Bus (SMBus) Specification Version 3.0
Table of Contents
1. Introduction ............................................................................................................................................. 8
1.1
Overview .................................................................................................................................... 8
1.2
Audience .................................................................................................................................... 8
1.3
Scope......................................................................................................................................... 8
1.4
Organization of this document ................................................................................................... 8
2. Related Documents And Reference Information .................................................................................... 9
2.1
Scope......................................................................................................................................... 9
2.2
Applicable Documents ............................................................................................................... 9
2.3
Reference Documents ............................................................................................................... 9
2.4
Definitions Of Terms ................................................................................................................ 10
2.5
Conventions ............................................................................................................................. 11
2.5.1
Numeric formats ...................................................................................................... 11
2.5.2
SMBus addresses ................................................................................................... 12
2.5.3
Transaction protocol diagrams ................................................................................ 12
3. General Characteristics ........................................................................................................................ 14
4. Layer 1 – The Physical Layer ............................................................................................................... 15
4.1
Electrical Characteristics Of SMBus Devices – Two Discrete Worlds .................................... 15
4.2
SMBus Common AC specifications ......................................................................................... 16
4.2.1
General timing conditions ........................................................................................ 21
4.2.2
Device timeout definitions and conditions ............................................................... 21
4.2.3
Master device clock extension definitions and conditions....................................... 21
4.2.4
Slave device clock extension .................................................................................. 22
4.2.5
SMBDAT low timeout .............................................................................................. 22
4.3
DC Specifications .................................................................................................................... 22
4.3.1
Supply voltage requirements ................................................................................... 23
4.3.2
SMBus branch circuit model ................................................................................... 23
4.3.3
Low Power DC parameters........................................................................................ 24
4.3.4
High Power DC specifications ................................................................................. 25
4.3.5
Additional common Low and High Power specifications......................................... 27
5. Layer 2 – The Data Link Layer ............................................................................................................. 28
5.1
Bit Transfers ............................................................................................................................ 28
5.1.1
Data validity ............................................................................................................. 28
5.1.2
START and STOP conditions ................................................................................. 28
5.1.3
Bus idle condition .................................................................................................... 29
5.2
Data Transfers On SMBus ...................................................................................................... 29
5.3
Clock Generation And Arbitration ............................................................................................ 30
5.3.1
Synchronization ....................................................................................................... 30
5.3.2
Arbitration ................................................................................................................ 31
5.3.3
Clock low extending ................................................................................................ 32
5.4
Data Transfer Formats ............................................................................................................ 34
6. Layer 3 – Network layer ........................................................................................................................ 34
6.1
Usage Model............................................................................................................................ 34
6.1.1
Master devices ........................................................................................................ 34
6.1.2
Slave devices .......................................................................................................... 35
6.1.3
Host ......................................................................................................................... 35
6.2
Device Identification – Slave Address ..................................................................................... 35
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