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
  • SUSPEND line
  • Power down/up
  • max. bitrate of 100 kbit/s


  • Tracii XL 2.0 is an interface and monitor offering support for the SMBus.