Chapter 14 Inter-Integrated Circuit (IICV3) Block Description
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
Freescale Semiconductor
565
14.7.1.7
Arbitration Lost
If several masters try to engage the bus simultaneously, only one master wins and the others lose
arbitration. The devices which lost arbitration are immediately switched to slave receive mode by the
hardware. Their data output to the SDA line is stopped, but SCL continues to be generated until the end of
the byte during which arbitration was lost. An interrupt occurs at the falling edge of the ninth clock of this
transfer with IBAL=1 and MS/SL=0. If one master attempts to start transmission while the bus is being
engaged by another master, the hardware will inhibit the transmission; switch the MS/SL bit from 1 to 0
without generating STOP condition; generate an interrupt to CPU and set the IBAL to indicate that the
attempt to engage the bus is failed. When considering these cases, the slave service routine should test the
IBAL first and the software should clear the IBAL bit if it is set.
