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SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
PMBus Interface/I2C Interface
Chapter 10
SNIU028A – February 2016 – Revised April 2016
PMBus Interface/I2C Interface
The UCD3138 family has a powerful and flexible PMBus/I2C interface. It has support for master mode, but
its primary use is in slave mode. Here are some of its features in slave mode:
•
Supports most I2C functions.
•
Designed to reduce CPU overhead
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Receives/Transmits up to 4 bytes at once
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Handles all PMBus sequencing in hardware
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Automatic Stop/Start sequence detection in hardware
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Provides automatic optimized clock stretching
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Automatic Acknowledge of Address, Command, and Data
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Can be used with polling alone, no interrupts needed
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Provides automatic PEC generation/checking
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Automatic hardware implementation of Alert arbitration
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Automatic Clock Low Timeout detection in hardware
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Address Mask permits automatic acknowledge of multiple addresses
•
Flexible
–
Supports polling and interrupt-driven firmware
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Can be configured to automatically acknowledge 1, 2, or 3 bytes of data at a time – on the fly.
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Auto or manual acknowledge of Address and Command bytes
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Supports 100 and 400 kHz
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Access to state of each PMBus Pin
•
Additional features supported on some devices
–
2 address registers permit automatic acknowledgement of any 2 addresses
–
2 PMBus/I2C interfaces on one device
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Clock High Timeout detection in hardware
–
Support for I2C in Master mode
Topic
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Page
10.1
PMBus Register Summary
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10.2
PMBus Slave Mode Initialization
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10.3
PMBus Slave Mode Command Examples
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10.4
Avoiding Clock Stretching
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10.5
PMBus Slave Mode Low Level Timing
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10.6
Effect of MAN_SLAVE_ACK bit on EOM Handling
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10.7
Master Mode Operation Reference
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10.8
PMBUS Communications Fault Handling
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10.9
Other Functions of the PMBus Module
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10.10 PMBus Interface Registers Reference
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