SLAZ437K October 2012 – May 2021 MSP430G2453 , MSP430G2453-Q1
USCI Module
Functional
I2C Mode Multi-master transmitter issue
When configured for I2C master-transmitter mode, and used in a multi-master environment, the USCI module can cause unpredictable bus behavior if all of the following four conditions are true:
1 - Two masters are generating SCL
And
2 - The slave is stretching the SCL low phase of an ACK period while outputting NACK on SDA
And
3 - The slave drives ACK on SDA after the USCI has already released SCL, and then the SCL bus line gets released
And
4 - The transmit buffer has not been loaded before the other master continues communication by driving SCL low
The USCI will remain in the SCL high phase until the transmit buffer is written. After the transmit buffer has been written, the USCI will interfere with the current bus activity and may cause unpredictable bus behavior.
1 - Ensure that slave doesn't stretch the SCL low phase of an ACK period
Or
2 - Ensure that the transmit buffer is loaded in time
Or
3 - Do not use the multi-master transmitter mode