USB-TO-GPIO datasheet(39/50 Pages) TI1

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B.1

Overview

B.2

Basic SMBUS Transaction Types Supported

B.3

Special Signals Used for PMBUS/SMBUS Communications

Appendix B

SLLU093 – August 2006

PMBUS/SMBUS Communications

This appendix describes the support for USB-to-PMBUS/SMBUS communications in

the USB Interface Adapter and how to use it for your applications.

The default firmware for USB Interface Adapter provides support for USB to PMBUS (revision 1.0) and

SMBUS (revision 2.0) communications. Similar to its I2C application, the USB Interface Adapter acts as a

PMBUS/SMBUS master, which can talk with one or multiple PMBUS/SMBUS slave devices daisy-chained

to a 10-pin ribbon cable.

Because PMBUS communication is derived from SMBUS communication, they share basic SMBUS

transaction types in common. These basic SMBUS transaction types include:

• Send byte

• Receive byte

• Write byte

• Read byte

• Write word

• Read word

• Block write

• Block read

• Process call

• Block read – block write process call

In addition, PMBUS communication also supports Group command.

All these commands are implemented in the USB Interface Adapter firmware.

Refer to Table 2-2 for special signal lines used for PMBUS/SMBUS communications.

Specifically, a slave device can assert an ALERT signal (by pulling it low) to report a fault or a warning

condition to the USB Interface Adapter; the host PC can obtain the ALERT signal by polling the USB

Interface Adapter. Note that the USB Interface Adapter does not support any Host Notify Protocol. This

means that the USB Interface Adapter cannot become a PMBUS/SMBUS slave and, therefore, cannot

support a slave to temporarily become a master and notify the host about the fault or the warning

condition.

For PMBUS communications, the USB Interface Adapter provides five CONTROL signals, each of which

can be used to enable/disable the powering up of one or multiple slave device(s).

Write Protect signal is not supported; neither is the RESET signal.

SLLU093 – August 2006

PMBUS/SMBUS Communications

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