Facts: SMBus

The System Management Bus (SMBus) is more or less a derivative of the I2C bus. The standard has been developed by Intel and is now maintained by the SBS Forum.

The main application of the SMBus is to monitor critical parameters on PC motherboards and in embedded systems. For example there a lot of supply voltage monitor, temperature monitor, and fan monitor/control ICs with a SMBus interface available.

There are some interesting differences between the I2C bus and the SMBus:

Packet Error Checking (PEC)
Timeout for transfers
Standardized transfer types
ALERT line
Power down/up
SUSPEND line

Tracii XL and Tracii XL 2.0 offer outstanding support for the SMBus.

Master

The I2C C++ and the I2C NET APIs of the I2C Framework contain several classes to support the SMBus master mode:

Calculation and checking of the PEC (CRC-8)
High-level interface to generate the standardized transfer types
Supports "block read" and similiar non-I2C-compatible transfer types (not supported by most other similar products claiming to be SMBus-compatible)
35ms timeout support

Using the SMBus master API it is possible to generate even complex SMBus messages with very few lines of code.

Tracer

I2C Studio offers several interesting features to analyse an SMBus with Tracii XL / Tracii XL 2.0:

Tracing of the ALERT and the SUSPEND lines
Tracing of power down and power up events
Checking of the PEC (CRC-8)
Trace plug-ins for common SMBus ICs (high-level analysing)