Intelligent Platform Management Bus

IPMB Description

The Intelligent Platform Management Bus or IPMB interface is based on the I2C bus and used as an interconnect between different boards within a chassis.
The IPMB interface is based on the I2C bus, as shown in the schematic graphic below.
The IPMB interface is used as an internal chassis bus that also interconnects to the external chassis-to-chassis interface; ICMB via a bridge chip.
The IPMB interface does include provisions for a connector, refer below.

The I2C bus uses a bi-directional Serial Clock Line [SCL] and Serial Data Lines [SDA]. Both lines are pulled high via a resistor [Rp]. Resistor Rs is optional, and used for ESD protection for 'Hot-Swap' devices. No other lines are specified. Three speed modes are specified: Standard; 100kbps [Bits per Second], Fast mode; 400kbps, High speed mode 3.4Mbps. I2C only communicates half-duplex. The maximum bus capacitance is 400pF, which sets the maximum number of devices on the bus and the maximum line length. The interface uses 8 bit long bytes, MSB [Most Significant Bit] first, with each device having a unique address. Any device may be a Transmitter or Receiver, and a Master or Slave. Data and clock are sent from the Master ~ valid while the clock line is high. The link may have multiple Masters and Slaves on the bus, but only one Master may be active at any one time. Slaves may receive or transmit data to the master.
VDD may be different for each device, but all devices have to relate their output levels to the voltage produced by the pull-up resistors [RP].

I2C Bus Interface Circuit
I2C Circuit Diagram

Also refer to the ICMB page for chassis to chassis communication.

I2C Bus Interface IC Manufacturers

Maxim {12-Bit Plus Sign Temperature Sensors with SMBus/I2C-Compatible Serial Interface}

NXP {I2C Bus}

Many ICs have the I2C interface including some processors and controllers.

IC Chip Manufacturers {All other types}

IPMB and I2C Standards Info

I2C-Bus Specification Version 2.1, Jan. 2000

Intelligent Platform Management Bus Communications Protocol Specification v1.0, Nov 15 1999

IPMB Connector

Connectors are used on the IPMB interface to include value added features. The interface is electrical interface is I2C.

Type A Pin Out
Signal namePin Number

The Type A connector is Molex part number 22-44-7031

Type B Pin Out
Signal namePin Number
3No connection

The Type B connector is Molex part number 22-44-7041

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Modified 2/4/12
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