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10.3.10 Arbitration
When several master devices simultaneously output a start condition (when STT is set to 1 before STD is set to
Note
1
), communication among the master devices is performed as the number of clocks are adjusted until the data
differs. This kind of operation is called arbitration.
When one of the master devices loses in arbitration, an arbitration loss flag (ALD) in the IIC status register (IICS0)
is set via the timing by which the arbitration loss occurred, and the SCL and SDA lines are both set for high
impedance, which releases the bus.
The arbitration loss is detected based on the timing of the next interrupt request (the eighth or ninth clock, when a
stop condition is detected, etc.) and the ALD = 1 setting that has been made by software.
For details of interrupt request timing, see "10.3.5 I
Note STD : Bit 1 of IIC status register (IICS0)
STT : Bit 1 of IIC control register (IICC0)
CHAPTER 10 SERIAL INTERFACE FUNCTION
2
C interrupt requests (INTIIC0)".
263
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