SLDM-06D1Ax

23

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Rev. AC

38. PMBUS INTERFACE CAPABILITY

The SLDM-06D1Ax power modules have a PMBus interface that supports both communication and control. The PMBus Power Management

Protocol Specification can be obtained from www.pmbus.org.The modules support a subset of version 1.1 of the specification (see Table 6 for a

list of the specific commands supported). Most module parameters can be programmed using PMBus and stored as defaults for later use.

All communication over the module PMBus interface must support the Packet Error Checking (PEC) scheme. The PMBus master must generate

the correct PEC byte for all transactions, and check the PEC byte returned by the module.

The module also supports the SMBALERT# response protocol whereby the module can alert the bus master if it wants to talk. For more

information on the SMBus alert response protocol, see the System Management Bus (SMBus) specification.

The module has non-volatile memory that is used to store configuration settings. Not all settings programmed into the device are automatically

saved into this non-volatile memory, only those specifically identified as capable of being stored can be saved (see Table 6 for which command

parameters can be saved to non-volatile storage).

39. PMBUS DATA FORMAT

For commands that set thresholds, voltages or report such quantities, the module supports the “Linear” data format among the three data formats

supported by PMBus. The Linear Data Format is a two byte value with an 11-bit, two’s complement mantissa and a 5-bit, two’s complement

exponent. The format of the two data bytes is shown below:

Data Byte High

7 6 5 4 3

2 1 0 7 6 5 4 3 2 1 0

Data Byte Low

Exponent

MSB

Mantissa

MSB

The value is of the number is then given by