Arbitration Lost - Motorola ColdFire MCF5281 User Manual

2
I C Programming Examples

24.6.7 Arbitration Lost

If several devices try to engage the bus at the same time, one becomes master. Hardware
immediately switches devices that lose arbitration to slave receive mode. Data output to
SDA stops, but SCL is still generated until the end of the byte during which arbitration is
lost. An interrupt occurs at the falling edge of the ninth clock of this transfer with
I2SR[IAL] = 1 and I2CR[MSTA] = 0.
If a device that is not a master tries to transmit or do a START, hardware inhibits the
transmission, clears MSTA without signalling a STOP, generates an interrupt to the CPU,
and sets IAL to indicate a failed attempt to engage the bus. When considering these cases,
the slave service routine should first test IAL and software should clear it if it is set.
24-14 MCF5282 User's Manual MOTOROLA