UCS1002-2 datasheet(30/114 Pages) MICROCHIP

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Programmable USB Port Power Controller with Charger Emulation

Datasheet

Revision 1.4 (07-16-13)

SMSC UCS1002

DATASHEET

bit, and it has been communicating with the SMBus protocol, it will reset its client interface and prepare

to receive further communications.

4.2.1.6

SMBus Timeout and Idle Reset

The UCS1002 includes an SMBus timeout feature. If the clock is held at logic ‘0’ for tTIMEOUT, the

device can timeout and reset the SMBus interface. The SMBus interface can also reset if both the

clock and data lines are held at a logic ‘1’ for tIDLE_RESET. Communication is restored with a start

condition. This functionality defaults to disabled and can be enabled by clearing the DIS_TO bit in the

Emulation Configuration register (see Section 10.4.2, "Emulation Configuration - 16h").

4.2.2

SMBus and I2C Compatibility

The major differences between SMBus and I2C devices are highlighted here. For more information,

refer to the SMBus 2.0 and I2C specifications.

1. UCS1002 supports I2C fast mode at 400 kHz. This covers the SMBus max time of 100 kHz.

2. Minimum frequency for SMBus communications is 10 kHz.

3. The SMBus client protocol will reset if the clock is held at a logic ‘0’ for longer than 30 ms. This

timeout functionality is disabled by default in the UCS1002 and can be enabled by clearing the

DIS_TO bit. I2C does not have a timeout.

4. Except when operating in Sleep, the SMBus client protocol will reset if both the clock and data

lines are held at a logic ‘1’ for longer than 200 µs (idle condition). This function is disabled by

default in the UCS1002 and can be enabled by clearing the DIS_TO bit. I2C does not have an idle

condition.

5. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).

6. I2C devices support block read and write differently. I2C protocol allows for unlimited number of

bytes to be sent in either direction. The SMBus protocol requires that an additional data byte

indicating number of bytes to read / write is transmitted. The UCS1002 supports I2C formatting only.

4.2.3

SMBus Protocols

The UCS1002 is SMBus 2.0 compatible and supports Write Byte, Read Byte, Send Byte, and Receive

Byte as valid protocols as shown below.

All of the below protocols use the convention in Table 4.3.

Table 4.3 Protocol Format

DATA SENT

TO DEVICE

DATA SENT TO

THE HOST

Data sent

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