SMBus

The System Management Bus (SMBus), derived from the I2C bus, is a bus system composed of two signals. Intel defined SMBus in 1995, encompassing Clock, Data, and instructions based on the Philips I2C serial bus protocol, with a clock frequency ranging from 10KHz to 100KHz.

Its primary applications include power management, temperature sensors, and EEPROM transmission in laptops.

In laptop applications, SMBus finds widespread use in power management systems. Through SMBus, laptops can effectively monitor and control aspects such as battery status, charging control, and energy management, contributing to enhanced battery life, optimized energy utilization, and ensured system stability.

Moreover, SMBus serves to connect temperature sensors, playing a crucial role in monitoring system temperature in laptops. This allows for fan control or other cooling measures as needed to ensure the system operates within a safe temperature range.

In terms of EEPROM transmission, SMBus provides a serial communication interface for reading and writing data in EEPROM. This functionality is vital for managing and configuring registers, including storing system settings and hardware information.

SMBus employs two main signal lines, SMBCLK (Clock), and SMBDATA (Data). SMBus typically operates at a voltage of 3V, ensuring normal operation while complying with the electrical characteristics and requirements of devices.

Logic Analyzer / MSO

TB3016E

TB3000 series Specifications PDF

MSO2116B (w/ analog channels)

MSO2000 series Specifications PDF

MSO3124V (w/ electrical validation)

MSO3000 series Specifications PDF

SMBus Decode

Show SBS (Smart Battery System)

Show SPD (Serial Presence Detect)

Save as TXT/CSV

In Logic Analyzer mode, click the icon above the report area to save the decoded data as a TXT/CSV file.

I2C Electrical Validation

Use an oscilloscope for I2C electrical validation to ensure compliance with defined specifications. After an extended burn-in test, the oscilloscope confirms that the electrical characteristics of the signal meet the required standards.

Supported Models: TS3124V (4-channel DSO), MSO3124V (4-channel DSO + 16-channel LA)

Electrical Validation Solution PDF

SMBus Decoding Setup Steps

1. Click Quick Settings or Add Protocol Decode to select a protocol for logic analyzer capture.

2. Select SMBus for decoding.

3. If you use Quick Settings, the system will recommend configurations for trigger type, sampling rate, voltage threshold, and channel settings.

4. Click the icon to access the Decode Settings screen.

Decode Settings

Channel

SMBCLK: Clock for SMBus data transmission.
SMBDATA: Data for SMBus data transmission.

Startup: Check whether to use PEC analysis.

Address: Show 8-bit addressing (include 7-bit addressing and 1-bit R/W).

Devices

MCTP: Show SMBus analysis in report area.
Show SBS (Smart Battery System): Show the Smart Battery System: voltage, electric current and the manufacturer.
Show SPD(Serial Presence Detect)：Report window show the configuration of memory module(DDR3, DDR2, DDR, SPD SDRAM) in EEPROM.

Ignore glitch: Ignore the glitch caused by slow transitions during analysis.

YouTube Videos

SMBus Decoding Examples