AMC6821 Reset I2C Hanging the Bus by Holding SDA Low

takishin

Other Parts Discussed in Thread: AMC6821

Our customer has a question about AMC6821.
I'm posting the question for the customer:

++++++++++++++++++++++++++++++++++++++++++++++

If the I2C(SMBus) port of AMC6821 is hanging the bus by holding SDA Low,
is the bus freed, by sending 9 clocks to the SCLK pin of the device
from master controller?

++++++++++++++++++++++++++++++++++++++++++++++

Thanks in advance.

Best regards,
Takishin

over 9 years ago

0 Matthew Sauceda over 9 years ago

TI__Genius 11750 points

Howdy Takishin,

Can you verify that the customer is writing '1' to bit 7 of configuration register 4? This is displayed in page 38 of the datasheet.

Best Regards,
Matt

0 takishin over 9 years ago in reply to Matthew Sauceda

Expert 2360 points

Hi Matt,

Thank you for your reply.

Yes. They know it.

They need a way of resetting the I2C bus of AMC6821 in the other case.

Can the I2C bus be reset by sending 9 clocks from a master device?

Best Regards,

Takishin

0 Matthew Sauceda over 9 years ago in reply to takishin

TI__Genius 11750 points

Howdy Takishin,

Thank you for the post. I'm currently awaiting feedback from design, and I wanted to say that I appreciate your patience. I've been traveling these past few weeks and I apologize for the lengthy delay. I will definitely try to provide a complete answer by Monday (Dallas time).

Best Regards,

Matt

0 Matthew Sauceda over 9 years ago in reply to Matthew Sauceda

TI__Genius 11750 points

Howdy Takishin,

Can you please describe the other case you are referring to? Writing '1' to bit 7 of configuration register 4 should always be applied for correct device operation.
If the customer is indeed setting this bit correctly, are they noticing that the I2C bus hangs because of the AMC6821 device?

Best Regards,

Matt

0 takishin over 9 years ago in reply to Matthew Sauceda

Expert 2360 points

Hi Matt,

Thank you for your cooperation.

I will ask our customer about that.

I understand that ｔhe device doesn't hang in right settings.

Best regards,
Takishin

0 takishin over 9 years ago in reply to takishin

Expert 2360 points

Hi Matt,

>Can you please describe the other case you are referring to?

The following situation is considered.

1. Host processor is reading I2C data from the FAN controller IC.
2. By some reasons, the host is reset while reading data.
3. Then I2C controller keeps the state of "Read" without timeout. (writing 1 to bit 7 of register 4)
4. After the host rebooting, the host accesses the I2C of the controller,
5. It cannot read the I2C data, because the controller keeps "low-level" on SDA. (I2C is hung.)

In this case, it needs the reset of I2C.

Best regards,
Takishin

0 Matthew Sauceda over 9 years ago in reply to takishin

TI__Genius 11750 points

Howdy Takishin,

If the host controller is reset, then to ensure correct communication with the AMC6821 device, it may be a good safety precaution to reset and re-write '1' to bit 7 of register 4.

- Does the host processor log any reset events, if so you can use this information to trigger a reset on the AMC6821 device, and re-initialize for proper communication.

Best Regards,

Matt

0 Matthew Sauceda over 9 years ago in reply to Matthew Sauceda

TI__Genius 11750 points

Howdy Takishin,

I was able to confirm that 9 clock cycles will recover the state of SDA.

Best Regards,
Matt

0 takishin over 9 years ago in reply to Matthew Sauceda

Expert 2360 points

Hi Matt,

Thank you for your reply.
It is a useful answer.

Best regards,
Takishin

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AMC6821 Reset I2C Hanging the Bus by Holding SDA Low